Only write to SERVER->status at the end of a monitoring loop

This makes the code clearer and reduces race conditions, as the monitor
could be writing SERVER->status while a router is reading it. Also,
the time during which the SERVER struct is locked drops to a fraction.

server/modules/monitor/mariadbmon/mariadbserver.hh

@@ -205,6 +205,16 @@ public:
      */
     bool is_down() const;
 
+    /**
+     * Convenience method for SERVER_IN_MAINT
+     */
+    bool is_in_maintenance() const;
+
+    /**
+     * Convenience method for SERVER_IS_RELAY_SERVER
+     */
+    bool is_relay_server() const;
+
     /**
      * Returns the server name.
      *
@@ -299,6 +309,20 @@ public:
      */
     void update_server(MXS_MONITOR* base_monitor);
 
+    /**
+     * Clear server pending status flags.
+     *
+     * @param bits Which flags to clear
+     */
+    void clear_status(uint64_t bits);
+
+    /**
+     * Set server pending status flags.
+     *
+     * @param bits Which flags to set
+     */
+    void set_status(uint64_t bits);
+
 private:
     void monitor_server(MXS_MONITOR* base_monitor);
     bool update_slave_status(std::string* errmsg_out = NULL);