audio: fix reacting on mic enable/disable requests

After getting an event of QubesDB FD, actually call qdb_read_watch() so
the event is cleared and the next one can be received.

Fixes QubesOS/qubes-issues#9619

pulse/pacat-simple-vchan.c

@@ -847,10 +847,19 @@ static void control_socket_callback(pa_mainloop_api *UNUSED(a),
 
     struct userdata *u = userdata;
     int new_rec_allowed = -1;
+    char *watch_path;
 
     if (!(f & PA_IO_EVENT_INPUT))
         return;
 
+    watch_path = qdb_read_watch(u->qdb);
+    if (!watch_path) {
+        pacat_log("Failed to read the qdb watch");
+        return;
+    }
+    /* don't bother checking which watch fired, there is just one */
+    free(watch_path);
+
     new_rec_allowed = is_rec_allowed_from_qdb(u);
     if (new_rec_allowed >= 0) {
         g_mutex_lock(&u->prop_mutex);