Fixes docstrings to be more accurate.

These docstrings were modified because they had the wrong path for the
config file and incorrect testing instructions. Since both files were
saying essentially the same thing it made sense to fix other parts of
the docstring to be similar.

Change-Id: Ibf48a369bbbe2c45dcf1d68305c83afe54bda7ff
Extract Assignment tests from IdentityTestCase

Extracts tests for domains, projects, roles and
grants/role assignments from IdentityTestCase
and put them in AssignmentTestCase.

Change-Id: I0e426fa1803e144b1c7a3eb503b212c6469e67c4
Closes-Bug: 1367778
Add xmlsec1 dependency comments

Right now, Keystone IdP uses xmlsec1 command line
tool to sign the generated SAML assertions:

https://github.com/openstack/keystone/blob/master/keystone/contrib/federation/idp.py#L369

If not installed, the command will fail.

Change-Id: I9d846c4d5913b7b711f540989c243371e1da2181
Merge "Extract Assignment tests from IdentityTestCase"
Merge "Fixes docstrings to be more accurate."
Merge "Add xmlsec1 dependency comments"