Change the pipeline of releasing to tag pipeline

Because zuul pre-release pipeline is pep400 compliant, but no
semver compliant, we can't push pre-release tags. Galaxy expects
from tags to be pure semver (not pep440).
Change the pipeline to be 'tag' and be triggered by any tag.

Change-Id: Ia288452668179723e35452d6e9579fb1dd0c4c3a

.zuul.yaml

@@ -453,6 +453,6 @@
         - ansible-collections-openstack-functional-devstack-rocky-ansible-2.11
         - ansible-collections-openstack-functional-devstack-queens-ansible-devel
 
-    pre-release:
+    tag:
       jobs:
         - ansible-collections-openstack-release

ci/publish/publish_collection.yml

@@ -24,6 +24,20 @@
         msg: "No tag was found in Zuul vars!"
       when: version_tag == 'no_version'
 
+    # Ansible Galaxy can accept only pure semver versions
+    # see https://semver.org for details
+    - name: Check that tag is proper semver
+      debug:
+        msg: >-
+          {{ version_tag is version('999.999.999', 'lt', version_type='semver') }}
+      ignore_errors: true
+      register: test_semver
+
+    - name: Fail if tag is not proper semver
+      fail:
+        msg: "Error is: {{ test_semver.msg }}"
+      when: test_semver is failed
+
     - name: Create a directory for collection
       file:
         state: "{{ item }}"