Faster swift-dispersion-populate

- Makes swift-dispersion-populate a bit faster when using a larger
  dispersion_coverage with a larger part_power.
- Adds option to only run population for container OR objects
- Adds option to let you resume population at given point (useful if you
  need to resume population after a previous run error'd out or the
  like) by specifying which suffix to start at.

The original populate just randomly used uuid4().hex as a suffix on the
container/object names until all the partition's required where covered.
This isn't a big deal if you're only doing 1% coverage on a ring with a
small part power but takes ages if you're doing 100% on a larger ring.

Change-Id: I52f890a774412c1d6179f12db9081aedc58b6bc2
Adding more unit tests for audit_location_generator

Change-Id: I40410fbbb79cea8647074f703e4675364c69d930
Add WWW-Authenticate to 401 responses

Per http://www.ietf.org/rfc/rfc2616.txt, when a 401 error is returned, the
Www-Authenticate response header MUST also be returned. The format is
described in http://www.ietf.org/rfc/rfc2617.txt.

Swift supports and/or implements a number of authentication schemes
including tempauth, Keystone, tempurl, formpost and container sync. In
this fix, we use a catch-all, "Swift". The realm is the account (where
known) or "unknown" (bad path or where the 401 is returned from code
that does not have the request). Examples:

     Www-Authenticate: Swift realm="AUTH_1234567889"
     Www-Authenticate: Swift realm="unknown"

Fixes bug #1215491

Change-Id: I03362789318dfa156d3733ef9348795062a9cfc4
Merge "Faster swift-dispersion-populate"
Merge "Adding more unit tests for audit_location_generator"
Merge "Add WWW-Authenticate to 401 responses"