Add 'openstack-db' tag to db-sync Exec resource

In order to make easy orchestration on all OpenStack db-sync, add this
tag so people can use this tag in composition layer.
A use case it to set some orchestration to make sure MySQL Galera is
ready before running any Exec with this tag.

Change-Id: I41a7eb38176781bffc16c6886a3de9f855036fbc
Closes-Bug: #1755102

manifests/db/create_schema.pp

@@ -26,6 +26,7 @@ class watcher::db::create_schema(
       Anchor['watcher::db::create_schema::begin']
     ],
     notify      => Anchor['watcher::db::create_schema::end'],
+    tag         => 'openstack-db',
   }
 
 }

releasenotes/notes/openstack_db_tag-8c7bcab4734ad950.yaml

@@ -0,0 +1,3 @@
+---
+features:
+  - Add openstack-db tag to Exec that run db-sync.

spec/classes/watcher_db_create_schema_spec.rb

@@ -17,6 +17,7 @@ describe 'watcher::db::create_schema' do
           'Anchor[watcher::db::create_schema::begin]'
         ],
         :notify      => 'Anchor[watcher::db::create_schema::end]',
+        :tag         => 'openstack-db',
       )
     end
 
@@ -40,6 +41,7 @@ describe 'watcher::db::create_schema' do
             'Anchor[watcher::db::create_schema::begin]'
           ],
           :notify      => 'Anchor[watcher::db::create_schema::end]',
+          :tag         => 'openstack-db',
         )
         }
       end