TT#65100 Fix double free for redis context on closure

We need to set the redis context to NULL after freeing it, otherwise
other code will try to free it again, which will make the program
abort when exiting.

Change-Id: Id634075344351eb1c924c59739b72bbf57de3c89

daemon/redis.c

@@ -672,6 +672,7 @@ err:
 static void redis_close(struct redis *r) {
 	if (r->ctx)
 		redisFree(r->ctx);
+	r->ctx = NULL;
 	mutex_destroy(&r->lock);
 	g_slice_free1(sizeof(*r), r);
 }