Updated openstack/openstack
Project: openstack-dev/devstack  db43b78ec569f1afa320677f34c999574b7126e4
null
make git_clone safer

the ensures that if the function returns early, we return to a
sane directory, and not hang out somewhere that a future git
call might modify a directory in a weird way. This is especially
important in the case of stable branches where were are hopping
between stable for servers and master for clients.

Change-Id: Ib8ebbc23b1813bc1bfb31d0a079f1b882135bd39