Fix issue preventing yagi from properly reauth-ing.

In atompub handler, UnauthorizedException was being imporoperly caught
by a general Exception error handler, preventing it from getting to
the code looking for it to trigger a re-auth.

Also, the force parameter in the yagi auth code was being ignored.

Fixed both of these.
Merge pull request #8 from rackerlabs/atompub_reauth_fix

Fix issue preventing yagi from properly reauth-ing.