Remove unused methods

The following methods are not used.
 o name() in nova/compute/power_state.py
    name() has been deleted in the following commit.

      commit 5270b0a565ec26d2f7de3a7d95be86433d8c6bd2
      Author: Dan Prince <dan.prince@rackspace.com>
      Date:   Wed Aug 17 11:46:28 2011 -0400

          Split set state into vm, task, and power state functions.

 o valid_states() in nova/compute/power_state.py
    valid_states() has been deleted in the following commit.

      commit 84e069b8d637c08f0434038ff2a2b272254e4a0e
      Author: Dan Prince <dprince@redhat.com>
      Date:   Mon Aug 6 12:09:23 2012 -0400

          Remove unused InstanceInfo class.

Change-Id: I85051d27834f166d5a3596e31ea4f78b82809fda
Merge "Remove unused methods"