V1 Boot from Volume snapshots overhaul

* Forbidden check for creating glance snapshot on BFV server
* Added creating volume from CBS snapshot fix
* Added clean up
* PEP8 check fixed issues
* removed double underscore

Change-Id: I34dd5c419e65f75e3161798098e1a172e7d795a9
Merge "V1 Boot from Volume snapshots overhaul"