object_event: reference state only if virEventAddTimeout succeeded

When registering new callback for an event, the event loop timer
must be created and registered. The timer has domain event state
object as an opaque argument which must be ref()-ed but only if
the timer was being created and registered successfully. We must
not ref it every time the virObjectEventStateRegisterID() runs.
Signed-off-by: NXu Yandong <xuyandong2@huawei.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel Henrique Barboza <danielhb413@gmail.com>

src/conf/object_event.c

@@ -891,19 +891,20 @@ virObjectEventStateRegisterID(virConnectPtr conn,
     virObjectLock(state);
 
     if ((state->callbacks->count == 0) &&
-        (state->timer == -1) &&
-        (state->timer = virEventAddTimeout(-1,
-                                           virObjectEventTimer,
-                                           state,
-                                           virObjectFreeCallback)) < 0) {
-        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                       _("could not initialize domain event timer"));
-        goto cleanup;
-    }
+        (state->timer == -1)) {
+        if ((state->timer = virEventAddTimeout(-1,
+                                               virObjectEventTimer,
+                                               state,
+                                               virObjectFreeCallback)) < 0) {
+            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                           _("could not initialize domain event timer"));
+            goto cleanup;
+        }
 
-    /* event loop has one reference, but we need one more for the
-     * timer's opaque argument */
-    virObjectRef(state);
+        /* event loop has one reference, but we need one more for the
+         * timer's opaque argument */
+        virObjectRef(state);
+    }
 
     ret = virObjectEventCallbackListAddID(conn, state->callbacks,
                                           key, filter, filter_opaque,