This commit is a whole new version of OSPurge. Currently OSPurge suffers
from the following limitations:
* It's slow (monothread)
* It's not guaranteed to complete. If a resource fails to be deleted then
OSPurge can choke on deleting other resources that depends on the first one.
* Not properly unit tested.
* Not modular (one huge file to deal with all services)
This new version is:
* Faster (multithreaded, thanks to a ThreadPoolExecutor)
* Safe (we check and wait for some prerequisites before attempting a
delete)
* 100% unit tested.
* Modular (one file per service)
Note that it's Python3.5 compatible. It also uses OpenStack Shade
and OpenStack client-config libraries so that OSPurge focuses on the
cleaning logic only.
Overall I believe this is a better version of OSPurge and more future
proof. NOte that we tagged and released OSPurge 1.3 recently in case
the new version was not satisfactory to everybody.
Change-Id: I5eb92a0556df210ea3cb4e471b8db3b5bf7ed5ee
3a612efd53