Use default Keystone API version in Devstack
Use default Keystone API version in Devstack

Right now devstack plugin has old workaround for python-manilaclient
that sets usage of Keystone v2 API for Manila requests.
So, remove it as it is not needed anymore since
python-manilaclient release 1.5.0 that supports Keystone API v3.

Change-Id: I42ce87ed6414b9048e49e24e5368a3f78c79acc5

vponomaryov/manila,vponomaryov/manila,openstack/manila,bswartz/manila,NetApp/manila,bswartz/manila,scality/manila,openstack/manila,scality/manila,NetApp/manila