Fix xenapi functions' tests

The tests got outdated, this fix makes the tests pass again.

Change-Id: Iadddfbf34bf79ba455811645e766c2f3d0fcca84
Workaround missing zip snapshot

At the moment, xenserver installation depends on github snapshots.
Unfortunately, git.openstack.org does not have that capability. This
fix includes:

 - Exit with error code, if a download fails
 - create proper urls, even if they are using the git protocol
 - set git base to github - so we are able to do snapshots

Fixes bug: 1259905

Change-Id: I8d0cf8bf8abb16ee0a4b138a6719409c75e7a146
Make unstack.sh more like stack.sh

unstack.sh and stack.sh both have to "configure projects", but the
code was different. This change makes it so the 2 sections of the
files are the same.

Change-Id: Ia06f8bbfbe2a6e87fb406e34e13a39bd7fa9e5af
Merge "Fix xenapi functions' tests"
Merge "Make unstack.sh more like stack.sh"
Merge "Workaround missing zip snapshot"