Fix keystoneauth with OPTIONS headers (eg: CORS)

- Fixes bug 1101143.

Change-Id: I2a82269e4aed2c8926e0aa736c38120784e25de2
Add wsgify and split_path utilities to swob

And refactor some of the code to use them.

Remove unused imports.

Change-Id: Ica479c10247fa85c740bb99cf7d1db7fbb1b2c80
Merge "Fix keystoneauth with OPTIONS headers (eg: CORS)"
Merge "Add wsgify and split_path utilities to swob"