ls-remote: simplify UNLEAK() usage

ls-remote: simplify UNLEAK() usage

We UNLEAK() the "sorting" list created by parsing command-line options
(which is essentially used until the program exits). But we do so right
before leaving the cmd_ls_remote() function, which means we have to hit
all of the exits. But the point of UNLEAK() is that it's an annotation
which doesn't impact the variable itself. We can mark it as soon as
we're done writing its value, and then we only have to do so once.

This gives us a minor code reduction, and serves as a better example of
how UNLEAK() can be used.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>