Honor security groups during provisioning

NC-200
Minor code formatting and dead code elimination

NC-200
Update instance security groups

Very ad-hoc implementation.
Waiting for DRF3.0 to fix serialization.

NC-200
Code review fixes

NC-200
Merge branch 'feature/nc-200' into 'develop'

Instance security groups, NC-200

Honor security groups during provisioning
Update them upon PUT/PATCH