Do hangups only after server states have been updated

The hangup code was refactored into a common function which should only be
used after the server states have been updated. This will remove erroneus
connections to already failed servers.

server/include/monitor.h

@@ -222,4 +222,13 @@ connect_result_t mon_connect_to_db(MONITOR* mon, MONITOR_SERVERS *database);
 void mon_log_connect_error(MONITOR_SERVERS* database, connect_result_t rval);
 void mon_log_state_change(MONITOR_SERVERS *ptr);
 
+/**
+ * @brief Hangup connections to failed servers
+ *
+ * Injects hangup events for DCB that are connected to servers that are down.
+ *
+ * @param monitor Monitor object
+ */
+void mon_hangup_failed_servers(MONITOR *monitor);
+
 #endif