git-p4: add trap to kill p4d on test exit
git-p4: add trap to kill p4d on test exit

Sometimes the "prove" test runner hangs on test exit because p4d is
still running. Add a trap to always kill "p4d" on test exit.

You can reproduce the problem by commenting "P4D_TIMEOUT" in
"lib-git-p4.sh" and running "prove ./t9800-git-p4-basic.sh".

Signed-off-by: Lars Schneider <5a28c51a1a2fd940035a2c87b954b4548c87165f@gmail.com>
Signed-off-by: Jeff King <696e3fbcf235d40b6ea1ebd61c87cbea79d444e7@peff.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git