Use override-checkout instead of override-branch

The former also makes sure to use the job definitions from the
respective branch, not only the source code.

Story: #2007282
Task: #38734
Change-Id: Id730b2d6bdd58da1fbe4c5fa24442281d5a69e5b

zuul.d/stable-jobs.yaml

@@ -1,7 +1,7 @@
 - job:
     name: ironic-standalone-train
     parent: ironic-standalone
-    override-branch: stable/train
+    override-checkout: stable/train
     vars:
       devstack_localrc:
         USE_PYTHON3: False
@@ -9,7 +9,7 @@
 - job:
     name: ironic-standalone-stein
     parent: ironic-standalone
-    override-branch: stable/stein
+    override-checkout: stable/stein
     vars:
       devstack_localrc:
         USE_PYTHON3: False
@@ -17,7 +17,7 @@
 - job:
     name: ironic-dsvm-standalone-rocky
     parent: ironic-standalone
-    override-branch: stable/rocky
+    override-checkout: stable/rocky
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc:
@@ -26,7 +26,7 @@
 - job:
     name: ironic-dsvm-standalone-queens
     parent: ironic-standalone
-    override-branch: stable/queens
+    override-checkout: stable/queens
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc:
@@ -38,17 +38,17 @@
 - job:
     name: ironic-tempest-functional-python3-train
     parent: ironic-tempest-functional-python3
-    override-branch: stable/train
+    override-checkout: stable/train
 
 - job:
     name: ironic-tempest-functional-python3-stein
     parent: ironic-tempest-functional-python3
-    override-branch: stable/stein
+    override-checkout: stable/stein
 
 - job:
     name: ironic-tempest-dsvm-functional-python3-rocky
     parent: ironic-tempest-functional-python3
-    override-branch: stable/rocky
+    override-checkout: stable/rocky
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc:
@@ -59,7 +59,7 @@
 - job:
     name: ironic-tempest-ipa-wholedisk-direct-tinyipa-multinode-train
     parent: ironic-tempest-ipa-wholedisk-direct-tinyipa-multinode
-    override-branch: stable/train
+    override-checkout: stable/train
     vars:
       devstack_localrc:
         USE_PYTHON3: False
@@ -67,7 +67,7 @@
 - job:
     name: ironic-tempest-ipa-wholedisk-direct-tinyipa-multinode-stein
     parent: ironic-tempest-ipa-wholedisk-direct-tinyipa-multinode
-    override-branch: stable/stein
+    override-checkout: stable/stein
     vars:
       devstack_localrc:
         USE_PYTHON3: False
@@ -75,7 +75,7 @@
 - job:
     name: ironic-tempest-dsvm-ipa-wholedisk-agent_ipmitool-tinyipa-multinode-rocky
     parent: ironic-tempest-ipa-wholedisk-direct-tinyipa-multinode
-    override-branch: stable/rocky
+    override-checkout: stable/rocky
     nodeset: openstack-two-node-xenial
     vars:
       devstack_localrc:
@@ -94,7 +94,7 @@
 - job:
     name: ironic-tempest-dsvm-ipa-wholedisk-agent_ipmitool-tinyipa-multinode-queens
     parent: ironic-tempest-ipa-wholedisk-direct-tinyipa-multinode
-    override-branch: stable/queens
+    override-checkout: stable/queens
     nodeset: openstack-two-node-xenial
     vars:
       devstack_localrc:
@@ -113,7 +113,7 @@
 - job:
     name: ironic-inspector-tempest-train
     parent: ironic-inspector-tempest
-    override-branch: stable/train
+    override-checkout: stable/train
     vars:
       devstack_localrc:
         FIXED_NETWORK_SIZE: 4096
@@ -123,7 +123,7 @@
 - job:
     name: ironic-inspector-tempest-stein
     parent: ironic-inspector-tempest
-    override-branch: stable/stein
+    override-checkout: stable/stein
     vars:
       devstack_localrc:
         FIXED_NETWORK_SIZE: 4096
@@ -133,7 +133,7 @@
 - job:
     name: ironic-tempest-dsvm-ironic-inspector-rocky
     parent: ironic-inspector-tempest
-    override-branch: stable/rocky
+    override-checkout: stable/rocky
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc:
@@ -144,7 +144,7 @@
 - job:
     name: ironic-tempest-dsvm-ironic-inspector-queens
     parent: ironic-inspector-tempest
-    override-branch: stable/queens
+    override-checkout: stable/queens
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc:
@@ -155,7 +155,7 @@
 - job:
     name: ironic-inspector-tempest-discovery-train
     parent: ironic-inspector-tempest-discovery
-    override-branch: stable/train
+    override-checkout: stable/train
     vars:
       devstack_localrc:
         USE_PYTHON3: False
@@ -163,7 +163,7 @@
 - job:
     name: ironic-inspector-tempest-discovery-stein
     parent: ironic-inspector-tempest-discovery
-    override-branch: stable/stein
+    override-checkout: stable/stein
     vars:
       devstack_localrc:
         USE_PYTHON3: False
@@ -171,7 +171,7 @@
 - job:
     name: ironic-inspector-tempest-dsvm-discovery-rocky
     parent: ironic-inspector-tempest-discovery
-    override-branch: stable/rocky
+    override-checkout: stable/rocky
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc:
@@ -180,7 +180,7 @@
 - job:
     name: ironic-inspector-tempest-dsvm-discovery-queens
     parent: ironic-inspector-tempest-discovery
-    override-branch: stable/queens
+    override-checkout: stable/queens
     nodeset: openstack-single-node-xenial
     vars:
       devstack_localrc: