gpg-interface: fix leak of "line" in parse_ssh_output()
We xmemdupz() this buffer, but never free it. Let's do so. We'll use a
cleanup label, since there are multiple exits from the function.
Note that it was also declared a "const char *". We could switch that to
"char *" to indicate that it's allocated, but that make it awkward to
use with skip_prefix(). So instead, we'll introduce an extra non-const
pointer.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>