Added debug print to place where changing DCB state fails.

server/core/dcb.c

@@ -1296,6 +1296,18 @@ static bool dcb_set_state_nomutex(
                         STRDCBSTATE(state),
                         STRDCBSTATE(dcb->state))));
         }
+        else
+        {
+                LOGIF(LD, (skygw_log_write(
+                                   LOGFILE_DEBUG,
+                                   "%lu [dcb_set_state_nomutex] Failed "
+                                   "to change state of DCB %p. "
+                                   "Old state %s > new state %s.",
+                                   pthread_self(),
+                                   dcb,
+                                   STRDCBSTATE(*old_state),
+                                   STRDCBSTATE(new_state))));
+        }
         return succp;
 }