If the default identity API version were to change
in devstack, the v2.0 tests would fail today,
resulting in a broken OSC gate.

Change-Id: Id634ea7e0fab9f3772383b5512ccac19f5119ac0

tempest-lib is deprecated, so replace it with tempest.lib.

Co-Authored-By: Sheel Rana <ranasheel2000@gmail.com>

Change-Id: I0495eba110bb7581623fbcf49dc63a27e9cb6d64
Closes-Bug: #1553047

This change replaces in many identity functests the pattern:

 raw_resource = create_resource(...)
 check(raw_resource)
 self.addCleanup(delete_resource, ...)
 ...

by the pattern:

 raw_resource = create_resource(...)
 self.addCleanup(delete_resource, ...)
 check(raw_resource)
 ...

which ensures that cleanup is defined and called after the test even if
check(resource) fails.

Change-Id: I4da541b7552d06eaffafda446e389bb552422cda

To make test cases more clearly, split test_identity.py
into test_user.py, test_role, etc. Add more test cases for
user, role, etc. Furthermore, to make functional tests run
repeatedly without raising duplicated error, clean up
resources before exiting each test case.

Change-Id: I1541943ad0b8d4d8d1e72822c159fda243b3d1d7
Implements: blueprint identity-functional-tests