git-upload-pack: make sure we close unused pipe ends

git-upload-pack: make sure we close unused pipe ends

Right now, we don't close the read end of the pipe when git-upload-pack
runs git-pack-object, so we hang forever (why don't we get SIGALRM?)
instead of dying with SIGPIPE if the latter dies, which seems to be the
norm if the client disconnects.

Thanks to Johannes Schindelin <redacted> for
pointing out where this close() needed to go.

This patch has been tested on kernel.org for several weeks and appear
to resolve the problem of git-upload-pack processes hanging around
forever.

Signed-off-by: H. Peter Anvin <redacted>
Signed-off-by: Junio C Hamano <redacted>