Remove oauth2 requirement

Since this patch was merged: https://review.openstack.org/#/c/64427/
Keystone now uses oauthlib instead of oauth2 as it's library for
OAuth related functions.

The previous oauth2 lib can now be removed from the global
requirements

Change-Id: Iba4beddc8d6e62d1657b68740fcca9d9a8fc7351
nova api validation fw requires jsonschema >= 2.0.0

The new nova api validation framework for v3 api uses methods (eg.
validators.extend) in jsonschema which are available starting in
version 2.0.0. The current min version is 1.3.0 and is incompatible
with the latest changes.

Change-Id: I943fd68b9fab3bce1764305a5058df5339470757
Partial-Bug: #1256344
Merge "nova api validation fw requires jsonschema >= 2.0.0"
Merge "Remove oauth2 requirement"