t5401: Use a bare repository for the remote peer

t5401: Use a bare repository for the remote peer

We want to avoid the warnings (or later, test failures) about
updating the current branch.  It was never my intention to have
this test deal with a repository with a working directory, and it
is a very old bug that the test even used a non-bare repository
for the remote side of the push operations.

This fixes the interleaved output error we were seeing as a test
failure by avoiding the giant warning message we were getting back
about updating the current branch being risky.

Its not a real fix, but is something we should do no matter what,
because the behavior will change in the future to reject, and the
test would break at that time.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>