Skip hostname checks and drop IP-based ACLs

* A reliable DNS setup cannot be assumed in MicroStack installations so
  relying on the host cache behavior of MySQL is not reliable. MySQL resolves
  an IP address to a host name and resolves that host name back to an IP
  address (https://dev.mysql.com/doc/refman/8.0/en/host-cache.html);
* IP addresses are not guaranteed to be static in a MicroStack
  deployment although this is preferable. Likewise, for services like
  cinder-volume to access the database on secondary nodes they need to
  be allowed to do that at the MySQL ACL level.

Change-Id: Ib87ab0a71fa83dad8e8ddb40f34907ab24999423

snap-wrappers/mysql/mysql-start-server

@@ -32,6 +32,8 @@ log-error=${LOGDIR}/error.log
 secure-file-priv=${FILESDIR}
 basedir=${BASEDIR}
 
+skip-name-resolve
+
 [mysql]
 socket=${RUNDIR}/mysqld.sock
 port=${PORT}

tools/init/init/questions/__init__.py

@@ -381,11 +381,11 @@ class DatabaseSetup(Question):
             ('placement', 'placement')
         ):
             db_password = db_creds[f'{service_user}-password']
-            sql("CREATE USER IF NOT EXISTS '{user}'@'{control_ip}'"
+            sql("CREATE USER IF NOT EXISTS '{user}'@'%'"
                 " IDENTIFIED BY '{db_password}';".format(
                     user=service_user, db_password=db_password, **_env))
             sql("CREATE DATABASE IF NOT EXISTS `{db}`;".format(db=db_name))
-            sql("GRANT ALL PRIVILEGES ON {db}.* TO '{user}'@'{control_ip}';"
+            sql("GRANT ALL PRIVILEGES ON {db}.* TO '{user}'@'%';"
                 "".format(db=db_name, user=service_user, **_env))
 
     def _bootstrap(self) -> None: