Some object comparsion syntax nits

[Zhongyue Luo]

There are some lines in nova where instead of "if X is not Y", it uses "if not X is Y"

Since "is not" seems to be the consensus and is more intuitive, object inequality evaluations should use "is not"

$ grep -R " not " nova | grep " is " | grep -E ":\W*if" | wc -lc
    315 22423
$ grep -R " not " nova | grep " is " | grep -v " is not " | grep -E ":\W*if" | wc -lc
     16 1301

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/20865

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/20865
Committed: http://github.com/openstack/nova/commit/e228035f442cf161af39202e931514528d6cab1a
Submitter: Jenkins
Branch: master

commit e228035f442cf161af39202e931514528d6cab1a
Author: Zhongyue Luo <email address hidden>
Date: Thu Jan 31 10:08:11 2013 +0800

    Fixes "is not" usage

    Fixes bug #1110973

    Change-Id: I68451ce32f3036e43a2bf1f59a02b392a9e40d6d