Fix persisted monitors not working

This prevented persisted monitors from being deleted after a restart.

include/maxscale/config.h

@@ -102,6 +102,7 @@ typedef struct config_context
     char                  *object;     /**< The name of the object being configured */
     CONFIG_PARAMETER      *parameters; /**< The list of parameter values */
     void                  *element;    /**< The element created from the data */
+    bool                   was_persisted; /**< True if this object was persisted */
     struct config_context *next;       /**< Next pointer in the linked list */
 } CONFIG_CONTEXT;