Deliver fake events for the current dcb immediately

If a fake event is added to the current dcb, we arrange things so
that it is delivered immediately when the handling of the event(s)
during which the fake event was added, has been performed.

Otherwise the event is delivered via the event loop.

include/maxscale/dcb.h

@@ -156,6 +156,7 @@ typedef struct dcb
     GWBUF           *delayq;        /**< Delay Backend Write Data Queue */
     GWBUF           *readq;         /**< Read queue for storing incomplete reads */
     GWBUF           *fakeq;         /**< Fake event queue for generated events */
+    uint32_t        fake_event;     /**< Fake event to be delivered to handler */
 
     DCBSTATS        stats;          /**< DCB related statistics */
     struct dcb      *nextpersistent;   /**< Next DCB in the persistent pool for SERVER */