MaaS service is no longer available: Should be removed

[shaderecker]

The MaaS (Migration as a Service) is no longer available. The corresponding code should be removed from the repo.
See here for mentions in code: https://github.com/opentelekomcloud/python-otcextensions/search?q=maas&unscoped_q=maas

[gtema]

Currently this is still a stub doing nothing. Anyway thks for the hint.