remote-hg: don't decode UTF-8 paths into Unicode objects

The internal mercurial API expects ordinary 8-bit string objects, not
Unicode string objects.  With this change, the test-hg.sh unit tests
pass again.

Signed-off-by: Richard Hansen <rhansen@bbn.com>
Reviewed-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>