git-remote-hg: use internal clone's hgrc

Use the hgrc configuration file in the internal mercurial repository in
addition to the other system wide hgrc files. This is done by using the
'ui' object from the 'repository' object which will have loaded the
repository hgrc file if it exists.

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