After "stop slave" times out, check replication status with "show slave status"

When executing "stop slave" with semisync replication, the replica server will tell the primary server that it's stopping replication. If the primary is down, this part can stall (even though this stall should be limited by rpl_semi_sync_slave_kill_conn_timeout). Other possible reasons for stalling could be an ongoing backup or FTWRL.

In some cases, this has caused MariaDB Monitor switchover/failover to time out. To deal with this, the monitor should check replication status with "show all slaves status" after "stop slave" has timed out. If replication status shows that slave threads have stopped, failover/switchover can proceeed.