remote-hg: test 'shared_path' in a moved clone

Since e71d1378 (remote-hg: fix 'shared path' path, 2013-12-07),
Mercurial 'shared_path' file is correctly updated whenever a clone is
moved. Make sure it keeps working, especially as this is depending on a
private Mercurial file.

Signed-off-by: Antoine Pelisse <apelisse@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>