Stop running test_schedule_to_all_nodes in the multinode job

After the recent changes we're running 5 tests already, some of them
using several VMs. This should cover scheduling to different conductors
well enough, the nova test just adds random failures on top.

This allows reducing the number of test VMs to 3 per testing node
(6 totally), reducing the resource pressure and allowing giving
each VM a bit more RAM.

Also adding missing VM_SPECS_DISK to the subnode configuration.

Conflicts:
	zuul.d/ironic-jobs.yaml

The Train backport also reduces concurrency to match master.

Change-Id: Idde2891b2f15190f327e4298131a6069c58163c0
(cherry picked from commit 1cb1df76d9)

zuul.d/ironic-jobs.yaml

@@ -356,8 +356,8 @@
       - zuul: opendev.org/zuul/zuul-jobs
     vars:
       tox_envlist: all
-      tempest_concurrency: 4
-      tempest_test_regex: "(ironic_tempest_plugin.tests.scenario|test_schedule_to_all_nodes)"
+      tempest_concurrency: 3
+      tempest_test_regex: "ironic_tempest_plugin.tests.scenario"
       tempest_test_timeout: 2400
       devstack_localrc:
         BUILD_TIMEOUT: 1200
@@ -387,10 +387,10 @@
         IRONIC_TEMPEST_BUILD_TIMEOUT: 600
         IRONIC_TEMPEST_WHOLE_DISK_IMAGE: True
         IRONIC_USE_LINK_LOCAL: True
-        IRONIC_VM_COUNT: 7
+        IRONIC_VM_COUNT: 3
         IRONIC_VM_EPHEMERAL_DISK: 0
         IRONIC_VM_LOG_DIR: '{{ devstack_base_dir }}/ironic-bm-logs'
-        IRONIC_VM_SPECS_RAM: 384
+        IRONIC_VM_SPECS_RAM: 512
         IRONIC_VM_SPECS_DISK: 4
         OVS_BRIDGE_MAPPINGS: 'mynetwork:brbm,public:br-infra'
         OVS_PHYSICAL_BRIDGE: brbm
@@ -462,11 +462,12 @@
           IRONIC_PROVISION_NETWORK_NAME: ironic-provision
           IRONIC_RAMDISK_TYPE: tinyipa
           IRONIC_USE_LINK_LOCAL: True
-          IRONIC_VM_COUNT: 7
+          IRONIC_VM_COUNT: 3
           IRONIC_VM_EPHEMERAL_DISK: 0
           IRONIC_VM_LOG_DIR: '{{ devstack_base_dir }}/ironic-bm-logs'
           IRONIC_VM_NETWORK_BRIDGE: sub1brbm
-          IRONIC_VM_SPECS_RAM: 384
+          IRONIC_VM_SPECS_RAM: 512
+          IRONIC_VM_SPECS_DISK: 4
           OVS_BRIDGE_MAPPINGS: 'mynetwork:sub1brbm,public:br-infra'
           OVS_PHYSICAL_BRIDGE: sub1brbm
           PHYSICAL_NETWORK: mynetwork