In every ansible task defined within upgrade_tasks it is
necessary to specify the tag 'tags' which are used during
the ansible execution for the upgrade_tasks serialization.
Adding the 'tags' check per upgrade_tasks step into
the YAML validation will allow us to catch if any
service upgrade task is missing this flag.
Change-Id: I8f56a87cc2e9ffc0d827bbb729f6bc3f6ca7550b
0be3317f45