Some fixes for 7.0 branch:
- fix docstrings to match sphinx requirements
- remove outdated 'tests_os_patching' module
- fix snapshot names for 6.1 -> 7.0 rollback/update jobs
- add separate groups for each of rollback/update jobs to reduce
amount of "skipped" test cases.
Change-Id: I4569db85099e4e3eb09b8b0d0a069fc243176f4c
Closes-Bug:#1468392
Related-Bug:#1470168