test-dirstate: use new `--docket` flag to get the data uuid stable

test-dirstate: use new `--docket` flag to get the data uuid

This is more robust.

Differential Revision: https://phab.mercurial-scm.org/D12592

--- a/tests/test-dirstate.t	Thu Apr 28 15:22:08 2022 +0200
+++ b/tests/test-dirstate.t	Thu Apr 28 16:24:55 2022 +0200
@@ -129,7 +129,7 @@
   > }
 
   $ find_dirstate_uuid () {
-  >   dirstate_data_files | sed 's#.hg/dirstate.##'
+  >   hg debugstate --docket | grep uuid | sed 's/.*uuid: \(.*\)/\1/'
   > }
 
   $ dirstate_uuid_has_not_changed () {