add some negative tests for tenant

making a separate test_tenant_negative.py,and move the exist negative
tests over to it,and add some negative tests for in it.

- test_update_non_existent_tenant
- test_tenant_update_by_unauthorized_user
- test_tenant_update_request_without_token

Change-Id: Id0d15d312c96a3f8a244d5e08414623e3c15013a
Merge "add some negative tests for tenant"