connect.c: ignore extra colon after hostname

connect.c: ignore extra colon after hostname

Ignore an extra ':' at the end of the hostname in URL's like
"ssh://example.com:/path/to/repo"

The colon is meant to separate a port number from the hostname.
If the port is empty, the colon should be ignored, see RFC 3986.

It had been working for URLs with ssh:// scheme, but was unintentionally
broken in 86ceb3, "allow ssh://user@[2001:db8::1]/repo.git"

Reported-by: Reid Woodbury Jr. <reidw@rawsound.com>
Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>