consolidate fix_auth#hardcode and recrypt 

- separate auth_model_spec and auth_config_model_spec
- call auth_model#recrypt from auth_config_model#recrypt

https://bugzilla.redhat.com/show_bug.cgi?id=1159009
Merge pull request #962 from kbrock/fix_auth_convert_v2

Simplify re-encrypt logic