GPFS Verify min release level for mmclone command

The gpfs driver makes heavy use of mmclone command.  This command
was added fairly recently.  Verify that the GPFS cluster is operating
at a level that supports mmclone at startup during prerequisite
checking in check_for_setup_error.

Need to verify:
1.  That gpfs cluster is at required level
2.  That filesystem(s) are also operating at required level.

Change-Id: Ie71d0b814d77b544e1a456d110882c1a02a5b2e5
Fixes: bug #1204266
Create key manager interface

This interface provides a thin wrapper around an underlying key
management implementation such as Barbican or a KMIP server. The key
manager interface is used by the volume encryption code to retrieve
keys for volumes.

This change is a copy-paste of the key manager interface accepted by
Nova. The major modifications are to the module imports (i.e.,
nova -> cinder).

Change-Id: I8f79165d66d67ad8faaca60946959c5a61811c59
Implements: blueprint encrypt-cinder-volumes
Merge "GPFS Verify min release level for mmclone command"
Merge "Create key manager interface"