Select stable/essex branches

The python-*client repos pick a commit from or before Essex release day.

Change-Id: Ia26d29f7b7da9dc6ffe81a88b2995b55ccfe8fe4
Add Apache 2 LICENSE file

Fixes bug 979172

Change-Id: Ifdfc22ad9348c6c6ae5a2c9380aae89328475056
Force prettytable==0.5

prettytable 0.6 was released recently and removed the printt() method.
All non-pinned prettytable projects (all of them) are now broken.  This
forces a pre-loaded prettytable 0.5 package in order to allow the real
fix (removing printt() calls) to proceed.

Change-Id: Iacf24b8474f12b28090329496720767281181d7e
Backport configure_tempest changes to stable/essex

Due to glance changes, it has a very simplistic method of getting the image url.

Change-Id: Ia1e524b049d8efddffa0461e14c0e2bb80c1812c
Backport new style XenServer install to essex

Change-Id: I1db76796a59f8040e88215fc452f6bb30037cf15
Merge "Backport new style XenServer install to essex" into stable/essex
Changed --user to --user_id and --role to --role_id in the keystone client for consistency. Need to update keystone calls here.

This change should be applied after [bug/994744 b7fe11c] in python-keystoneclient.

Fixes bug 994744.

stable/essex note: keystoneclient trunk is used by stable/essex devstack
because there aren't stable branches for client libraries so we need
this change to pass devstack gate, currently failing with:
keystone user-role-add: error: ambiguous option: --user could match
--user-id, --user_id

Change-Id: I13e643f8552d86ed0bf92799271899f777bde9b2
Fix bug 1020513 by downloading xenapi plugins from correct place

Cherry picked from:
https://review.openstack.org/#/c/9263/

Change-Id: I2fc9c55b444bac355347f0d53b5971d4b809fbff
Fix multiple distro dependency bug

get_packages() icorrectly handled multiple distros listed in a dependency
file, such as:

    xyz  # dist:fred,barney,wilma

Change-Id: Ib1178b2aaaddafe581902b32776180bb0b41f1ae
(cherry picked from commit 3ea11129012b9ffdf5f38724e11fa9efda9362f5)
Add flag for availablility of change password API.

Change-Id: Ic63754050ef4a5838144edd1d24a2e9206cc0fa5
add TENANT_ARG to swift command line.

Fix bug 1020985.

Cherry-picked from https://review.openstack.org/#/c/9318/

Change-Id: Ibef5b975bdf95250a069797594d010eeb102ecae
Use apt git package instead of git-core.

The git-core package is deprecated in favor of the git package. Use the
git package instead.

Change-Id: Ib136e34c7a0d4f87b02e32996420b3f507ca0bf4