remote-hg: fix test

It wasn't being checked properly before; those refs never existed.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
transport-helper: don't update refs in dry-run

The remote helper namespace should not be updated.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-hg: improve arithmetic evaluation in test

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>