Fixed issue when savanna url is not provided

* Now savannaclient takes savanna_url is as follows:
  https://HOST:PORT/VERSION/PROJECT_ID
  IMPORTANT! This URL pattern and only this is valid for client now.

* Old URL pattern 'https://HOST:PORT/VERSION' is no longer valid and
  exception will be rised on attempt to connect to 'data_processing'
  service

* Why this needed, because it's common OS approach:
  - base.url_for(ctx.service_catalog, 'data_processing') returns
    https://HOST:PORT/VERSION/PROJECT_ID
  - This bug blocks impl of bp savanna-as-heat-resource
  - Here we recieve https://HOST:PORT/VERSION/PROJECT_ID
    https://github.com/openstack/python-savannaclient/blob/master/savannaclient/api/client.py#L60

Change-Id: Iba98d2a57c0aa7900e3b4ec8bbc69b198e933db4
Closes-Bug: #1274913
Merge "Fixed issue when savanna url is not provided"