Makes ansible fail if login_port is defined and login_host is either not...

... defined, or defined as localhost. This is because if login_host is localhost then MySQLdb will use the socket instead of TCP. This leads to confusion for ansible users as, when a port is defined it gets ignored if login_host is localhost. This is to fix the bug reported by wrosario #8070. Info on MysqlDb can be read here http://mysql-python.sourceforge.net/MySQLdb.html