use expected_length parameter to assert expected length

assertValidRoleAssignmentListResponse method provides expected_length
parameter to assert expected length of list response. However, we
do not use it.

Change-Id: Ifc9ff3f13809ef939d2154d1ddd8648735efb613
Update keystone readme to point to specs.o.org

There is at least one dead link in the README, and a few links to
the old identity-api on github.com. These should be linked to
specs.o.org/keystone-specs

Change-Id: Ida6eb0a48ff2f2518d3352624cc461c9ff2c458f
Updated from global requirements

Change-Id: I8d7508dac151e3854971588b5d0376afb6d95cd8
Merge "use expected_length parameter to assert expected length"
Merge "Update keystone readme to point to specs.o.org"