Previously if you wanted to use the openstack::db::mysql for to create a
database and use the same user for multiple databases, the catalog would
fail due to a duplicate mysql_user definition. This change adds the
ability to disable the user creation as well as the grant if the user
does not need it.
Change-Id: Id04a622cc900254fe60bc257a9e42d16c676bf40
Related-Bug: 1649341