Adding test cases for more coverage

Change-Id: I92a25f2348aae1100af8172c9db70ab34b1595c1
Increased common/utils.py test coverage to 100%

Change-Id: Ia914b6ae6303bf47b35c49dad35e21274109e0a7
Add dogtag plugin to new plugin structure

This patch adds the dogtag plugin (and tests) to the new plugin
structure under plugins/ and converts the plugin to an implementation
of the SecretStore interface.

The old dogtag_crypto_plugin will be retained until the top level
plugin manager and resources have been switched over, allowing us to
fully test the new dogtag plugin.

Change-Id: I20e2daca6dad2339d228e850a03868ac587089c0
Merge "Increased common/utils.py test coverage to 100%"
Merge "Add dogtag plugin to new plugin structure"
Merge "Adding test cases for more coverage"
editing for gramatical and english errors

Change-Id: I39e1cf8bc3e64b3fff90075e77afb8c65a1cf646
Merge "editing for gramatical and english errors"