This patch adds a user authentication of incoming request.

A new option enable_authentication is introduced in solum.conf
to control incoming request authentication via keystone. By default this
option has value True.
If this option is enabled (has value True) a keystoneclient.auth_token
middleware will be installed.

test_functional.py file has beed removed as it is not
compatible with authentication changes. Tests from test_functional file
will be added to functionaltest folder by a separate commit.

This patch adds python_keystoneclient into requirements.txt
Change-Id: I16aa0ba66eb8f5bf74e955245baba43118c89057
Implements: blueprint user-authentication
Merge "This patch adds a user authentication of incoming request."