builtin-push: don't access freed transport->url

builtin-push: don't access freed transport->url

Move the failed push message to before transport_disconnect() so that
it doesn't access transport->url after transport has been free()'d (in
transport_disconnect()).

Additionally, make the failed push message more accurate by moving it
before transport_disconnect(), so that it doesn't report errors due
to a failed disconnect.

Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Acked-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>