MDEV-16495 mariadb segfaults at start on FreeBSD

don't use MY_MUTEX_INIT_FAST in constructors of statically
allocated objects.

sql/semisync_master_ack_receiver.cc

@@ -43,8 +43,7 @@ Ack_receiver::Ack_receiver()
   DBUG_ENTER("Ack_receiver::Ack_receiver");
 
   m_status= ST_DOWN;
-  mysql_mutex_init(key_LOCK_ack_receiver, &m_mutex,
-                   MY_MUTEX_INIT_FAST);
+  mysql_mutex_init(key_LOCK_ack_receiver, &m_mutex, NULL);
   mysql_cond_init(key_COND_ack_receiver, &m_cond, NULL);
   m_pid= 0;