stop calling UNLEAK() before die()

stop calling UNLEAK() before die()

The point of UNLEAK() is to make a reference to a variable that is about
to go out of scope so that leak-checkers will consider it to be
not-leaked. Doing so right before die() is therefore pointless; even
though we are about to exit the program, the variable will still be on
the stack and accessible to leak-checkers.

These annotations aren't really hurting anything, but they clutter the
code and set a bad example of how to use UNLEAK().

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