mysql_replication should not connect to the 'mysql' database

All the actions by the mysql_replication plugin can be done by connecting to the NULL database. There is no need to connect to the 'mysql' db, since there are permissions problems when connecting to remote hosts, e.g. when you want to query "SHOW MASTER STATUS" on a remote host.
Merge pull request #16 from kustodian/mysql_replication_no_mysql_db

mysql_replication should not connect to the 'mysql' database