Make sure proposal validations do not break install

This references PR #894 and BNC #860117
Do not run validations from within the apply_role
Skip after_save validation on creating proposals

And add comment explaining why
Ensure backwards compatibility in transition

If a barclamp returns [status, node.to_hash], pass it along.
Merge pull request #946 from bkutil/fix/proposal_validations

Fix/proposal validations
Merge pull request #947 from bkutil/fix/backward_compatibility_in_transition

Ensure backwards compatibility in transition