Support token based auth options for osc
Support token based auth options for osc

Currently, the searchlightclient osc plugin assumes the presence of
auth_url, username, password options when creating the SL client object.
It should support passing --os-token (OS_TOKEN) and --os-url (OS_URL) to
openstackclient, which skips token generation and catalog retrieval.

Change-Id: Ied8f32c18e6e25130e14e37a170c786bc5a90f29
Closes-bug: #1539260

openstack/python-searchlightclient,openstack/python-searchlightclient