update requires to prevent version cap

OpenStack clients requirements should not have an upper bound
as that has implications for testing in the gate.

ref: https://github.com/openstack/requirements

fixes bug #1200214
Change-Id: I45c8e94ede892a4d5412ac43aae9c4e131907c89
Merge "update requires to prevent version cap"
Support token_format for backward compatibility

The provider property in the [token] section will be unset by default. If
provider is not set, we will use token_format in the [signing] section to
determine to provider. If provider is set, it must agree with the token_format.

fixed bug 1202651

Change-Id: I15ff67490acbbacc9eefc7eee253400475704b04