block: Release allocated options after bdrv_open

They aren't used afterwards nor supposed to be stored by a bdrv_create
handler.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -540,6 +540,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
         }
 
         ret = bdrv_create(bdrv_qcow2, tmp_filename, options);
+        free_option_parameters(options);
         if (ret < 0) {
             return ret;
         }