Move nova cells db sync into nova-api profile

Move nova cells db sync into nova-api profile

Having the db_sync code live in the mysql profile causes
coupling that doesn't work unless your MySQL server has the
latest Nova packages installed. This may not work for some
baremetal setups (where an isolated database exists) or
with containers where the MySQL container definately doesn't
have nova packages installed.

Moving this code into the nova-api role also matches where we
were already db syncing the normal API database so it should be
fine and safe.

Change-Id: Ib625e2ac9c8d6bd1d335c58e291facc4ea5839ae
Co-Authored-By: Alex Schultz <aschultz@redhat.com>