Remove swiftclient dependency

Removes the requirement for swiftclient in swift-dispersion-report
and swift-dispersion-populate. To prevent a dependency on
keystoneclient and to avoid reinventing the wheel with an internal
keystoneclient, authentication with keystone is only supported if
swiftclient is available. If not, only auth v1 is supported.

The dependency in swift/container/sync.py has also been removed.

Implements: blueprint remove-swiftclient-dependency

Change-Id: I6ec3b3c85a67b9ab6eb04b90ffc16daf1600e8a7
Merge "Remove swiftclient dependency"