Allow passing in explicit version for legacy_client
Allow passing in explicit version for legacy_client

Nova (and indeed other clients with microversions, need a user to be
able to request an explicit version.

Change-Id: I5f67b7fc007b7d6123f621c5943345f88db1f84b

dtroyer/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk,openstack/python-openstacksdk,openstack/os-client-config,dtroyer/python-openstacksdk,stackforge/python-openstacksdk,dtroyer/os-client-config