Proposing a change to remove user validation tests

As per discussions from bug
https://bugs.launchpad.net/keystone/+bug/999084 and
patch https://review.openstack.org/#/c/27593/

am proposing a change to remove these tests since

1. Passwords are optional
2. No restriction on the length of the password
3. Since password checks are optional, it doesn't make sense to check
email format as well.
4. May be these checks should be in nova unit tests as and when a
consensus on these validation standards are met.

As of now, it doesn't make sense to have these tests in tempest.

Change-Id: I5ac3a1df2f7b0241a0077a252c240da361ed10d3
Merge "Proposing a change to remove user validation tests"