add token test for token-api

- test_tokens.py

Change-Id: I1dad4a32ab22c39f37ad77913781cc3ed55590fe
add test for updating server's disk_config test

this add test for updating server's disk_config tests. And use
addCleanup to manager server resource instead of deleting server
at end of these tests in this file.

Change-Id: I2ed90456e86f6e8c6e7d0b954bf381d944a6ca53
Merge "add token test for token-api"
Merge "add test for updating server's disk_config test"