block/blkdebug: fix memory leak

Spotted by PVS-Studio

Signed-off-by: Elena Afanasova <eafanasova@gmail.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1e903f928eb3da332cc95e2a6f87243bd9fe66e4.camel@gmail.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

block/blkdebug.c

@@ -215,6 +215,7 @@ static int add_rule(void *opaque, QemuOpts *opts, Error **errp)
                                  BLKDEBUG_IO_TYPE__MAX, &local_error);
         if (local_error) {
             error_propagate(errp, local_error);
+            g_free(rule);
             return -1;
         }
         if (iotype != BLKDEBUG_IO_TYPE__MAX) {