Pass in GIT_BASE when calling stack.sh

since ./stack.sh is called as a binary, $GIT_BASE needs to be passed in
to override devstack's default GIT_BASE.

And add comment about git.openstack.org

Change-Id: I55482a387fe54235baba90e7b83837f7cb5b4bc6
Change default GIT_BASE to git.openstack.org

Instead of cloning from github, which ratelimits use our own
official git.openstack.org mirrors.

This change doesn't affect the gate as the images are pre-populated.

Change-Id: Ic12fbace0d54f7c624140410e2a2c1f5f8264d47
Add n-cond to list of nova processes to kill

n-cond was missing from the list of nova processes.

(plucked from gate)

Change-Id: I7aceff852de82b7e70294cf069c21d3399b27020
also skip bundle and euca

these exercises don't work on many versions of boto, stop using
them by default in grenade.

Change-Id: Idca068b0f062c31963d7c32d88f5721343b5c0cd
do xtrace in include scripts correctly

the included upgrade scripts were turning off xtrace, not
restoring it like we should have been doing. This makes debugging
many of the upgrade issues very difficult.

fix this with the standard xtrace restore.

Change-Id: I922d139b83644a2584c46fecb51b346b05feeec8
Merge "Pass in GIT_BASE when calling stack.sh"
Merge "Change default GIT_BASE to git.openstack.org"
Merge "Add n-cond to list of nova processes to kill"