Publish weekly

To better utilise caches during the working week, we decided
to publish only weekly (as opposed to daily).
This is due to DockerHub-imposed limits.

Change-Id: Ib4710dae09e991c0ad21c44a64b2617e0fd4fdc6

.zuul.d/centos.yaml

@@ -35,7 +35,7 @@
               - ^requirements.txt$
               - ^setup.cfg$
               - ^setup.py$
-    periodic:
+    periodic-weekly:
       jobs:
         - kolla-publish-centos-source
         - kolla-publish-centos-binary

.zuul.d/debian.yaml

@@ -5,7 +5,7 @@
         - kolla-build-debian-source
         - kolla-build-debian-binary
         - kolla-ansible-debian-source
-    periodic:
+    periodic-weekly:
       jobs:
         - kolla-publish-debian-source
         - kolla-publish-debian-source-aarch64

.zuul.d/ubuntu.yaml

@@ -13,7 +13,7 @@
         - kolla-build-ubuntu-source
         - kolla-ansible-ubuntu-source
         - kolla-ansible-ubuntu-source-upgrade
-    periodic:
+    periodic-weekly:
       jobs:
         - kolla-publish-ubuntu-source
         - kolla-publish-ubuntu-binary