REST API return traceback

[Sergey Reshetnyak]

Steps to reproduce:
1. Start Savanna.
2. Send REST request:
http://savanna/v1.0/tenant/
Result:
Response code: 500
Body:
Traceback (most recent call last):
  File "/home/serg/projects/savanna/.tox/venv/lib/python2.7/site-packages/eventlet/wsgi.py", line 384, in handle_one_response
    result = self.application(self.environ, start_response)
  File "/home/serg/projects/savanna/.tox/venv/lib/python2.7/site-packages/flask/app.py", line 1701, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/serg/projects/savanna/.tox/venv/lib/python2.7/site-packages/keystoneclient/middleware/auth_token.py", line 458, in __call__
    return self.app(env, start_response)
  File "/home/serg/projects/savanna/.tox/venv/lib/python2.7/site-packages/savanna/middleware/auth_valid.py", line 49, in __call__
    version, url_tenant, rest = commons.split_path(path, 3, 3, True)
  File "/home/serg/projects/savanna/.tox/venv/lib/python2.7/site-packages/savanna/openstack/commons.py", line 55, in split_path
    raise ValueError('Invalid path: %s' % path)
ValueError: Invalid path: /v1.0/11587919cc534bcbb1027a161c82cf58

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/37255