Adds delete_volume_attachment method to behaviors for attach api.

 * New method waits for volume attachment to return a 404 after
   issuing a delete.
 * Minor pep8 cleanup of the behaviors module.
 * Cleaned up some error message formatting.

Change-Id: I33d89d17dd900d18677b8a8c7b58d7432111dfc5
Raise NotImplementedError instead of NotImplemented

NotImplementedError is the name of the exception
(https://docs.python.org/2/library/exceptions.html).

NotImplemented is the name of a constant
(https://docs.python.org/2/library/constants.html).

It makes no sense to raise a constant. The exception should
be raised instead.

Change-Id: I369b47dac60106f96aed9d044f8b510afd09d266
Closes-Bug: #1339855
Improved MemoizedAuthServiceComposite

 * service property raises an exception if no service is found
 * public_url property raises an exception if not endpoint is found
   in the targeted service.
 * Memoization works correctly for same-credentials/different auth
   systems scenario now.
 * Memoization works correctly when passing instantiated configs
   into the __init__ now.
 * Memoization works for switching credentials by changing the
   configs being used in the same composite now, although this
   isn't recommended.
 * Removed _lazy_property class
 * All properties now properly check the current cached version
   of the access data, instead of caching the first version
   accessed.

Change-Id: I96b720dc6479569dcd9eae793d9993df9bcde00c
Merge "Improved MemoizedAuthServiceComposite"
Merge "Adds delete_volume_attachment method to behaviors for attach api."