upload-pack: make check_non_tip() clean things up on error

upload-pack: make check_non_tip() clean things up on error

On error check_non_tip() will die and not closing file descriptors is no
big deal. The next patch will split the majority of this function out
for reuse in other cases, where die() may not be the only outcome. Same
story for popping SIGPIPE out of the signal chain. So let's make sure we
clean things up properly first.

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
Signed-off-by: Junio C Hamano <redacted>