Skip watcher containers for downstream

Watcher related packages got added in RDO antelope but not available in
OSP-18 downstream.

openstack-k8s-operators/tcib#215 adds watcher
container in tcib. Since downstream tcib jobs install the tcib rpm from
main branch so it may break downstream container build and component
job.

So in order to avoid breakage, we are skip building watcher related
containers.

Note: It also fixes the exclude conditional to check existence of
release key in exclude var to avoid following error:
```
''dict object'' has no attribute ''master'''
```

Depends-On: openstack-k8s-operators/tcib#215

Signed-off-by: Chandan Kumar <[email protected]>

Author: raukadah

roles/build_containers/defaults/main.yml

@@ -55,3 +55,12 @@ cifmw_build_containers_install_from_source: false
 # cifmw_build_containers_dockerfile_labels
 # cifmw_build_containers_extra_config
 # cifmw_build_containers_build_timeout
+
+# Note(Chandankumar): Remove it once watcher related packages are available downstream.
+cifmw_build_containers_exclude_containers:
+  rhos18:
+    rhel9:
+      - watcher-base
+      - watcher-api
+      - watcher-applier
+      - watcher-decision-engine

roles/build_containers/templates/build_containers.sh.j2

@@ -22,7 +22,7 @@ openstack tcib container image build \
 {%   if cifmw_build_containers_rhel_modules is defined %}
      --rhel-modules {{ cifmw_build_containers_rhel_modules | join(",") }} \
 {%   endif %}
-{%   if cifmw_build_containers_exclude_containers is defined %}
+{%   if cifmw_build_containers_exclude_containers is defined and cifmw_build_containers_openstack_release in cifmw_build_containers_exclude_containers %}
 {%   set distroversion = cifmw_build_containers_distro + cifmw_build_containers_dist_major_version %}
 {%   for item in cifmw_build_containers_exclude_containers[cifmw_build_containers_openstack_release][distroversion] %}
      --exclude {{ item }} \