Raise/Relax WebTest requirement to match Keystone

All OpenStack modules I can find are using an unbounded
WebTest test-requirement, and at least Keystone fails gating
with 1.3.3. Raise requirement to 2.0, which seems to match reality.

Change-Id: I7ffef924f93256b9d8d6191b5f79de937b05e2b0
os/requirements should be in sync with itself

Change-Id: I15800030c932ddaa1a9b9037bc10fc3356f8efd6
Merge "Raise/Relax WebTest requirement to match Keystone"
Merge "os/requirements should be in sync with itself"