MXS-1703 Failover launch code cleanup

Removed one field from MXS_MONITOR, as it was only used by mariadbmon and is
unnecessary (the case it handled was impossible).

include/maxscale/monitor.h

@@ -219,7 +219,6 @@ struct mxs_monitor
     bool active; /**< True if monitor is active */
     time_t journal_max_age; /**< Maximum age of journal file */
     uint32_t script_timeout; /**< Timeout in seconds for the monitor scripts */
-    bool master_has_failed; /**< Set to true when the latest event is a master_down event */
     uint8_t journal_hash[SHA_DIGEST_LENGTH]; /**< SHA1 hash of the latest written journal */
     struct mxs_monitor *next;     /**< Next monitor in the linked list */
 };