remove the impression of unexpectedness when access is denied

remove the impression of unexpectedness when access is denied

If a server accessed through ssh is denying access git will currently
issue the message

	"fatal: The remote end hung up unexpectedly"

as the last line. This sounds as if something really ugly just happened.
Since this is a quite typical situation in which users regularly get
we do not say that if it happens at the beginning when reading the
remote heads.

If its in the very first beginning of reading the remote heads it is
very likely an authentication error or a missing repository.

If it happens later during reading the remote heads we still indicate
that it happened during this initial contact phase.

Signed-off-by: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>