remote-hg: trivial cleanups

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-hg: make sure fake bookmarks are updated

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-hg: properly report errors on bookmark pushes

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