fixes #2455 hostgroup not saving
fixes #2393 - Couple of models broken with audited 3.0.0

this is not a fix for the mass assignment problem, rather just to solve immedient packaing issue upstream.

a follow up on mass assignment should be done via another commit.
fixes #2424 encrypts compute resource password

SETTINGS[:encryption_key] is required

rake db:compute_resource:encrypt
rake db:compute_resource:decrypt