test: mark rhg output as flaky

rhg is not updating the dirstate on status yet, which make this part of the test
flaky. This will be fixed soon.

Differential Revision: https://phab.mercurial-scm.org/D11833

tests/test-backout.t

@@ -172,7 +172,9 b' transaction: in-memory dirstate changes '
   $ hg status -A
   C c
   $ hg debugstate --no-dates
-  n 644         12 set                 c
+  n 644         12 set                 c (no-rhg !)
+  n 644         12 unset               c (?)
+  n 644         12 set                 c (?)
   $ hg backout -d '6 0' -m 'to be rollback-ed soon' -r .
   removing c
   adding b