Currently there isn't a uniform or easily expandable way to manage
how Pegleg gets credentials or enforces any complexity on them. This
patchset attempts to address this by:
1. Moving all logic for credentials into config.py
2. Using PeglegSecretManagement as the source of interfacing with
config.py as this code is the entry point for any encryption or
decryption work
3. Remove unnecessary code related to this change
4. Update unit tests
In future patchsets the goal is to use these changes to add in a global
passphrase and salt variable into config.py so that encrypt/decrypt type
commands can be executed one time against a site and intelligently
handle retrieval of global credentials for use with global secrets, site
credentials in the form of environment variables will remain used for
site secrets and will not be overridden by any global operations.
Change-Id: I0b6acd3ef5eab6b1f8931f46544bc53443f5c2c0
ea99c79844