PEP8 quantum cleanup

[Zhongyue Luo]

The None, True, and False values are singletons.

All variable *comparisons* to singletons should use 'is' or 'is not'.
All variable *evaluations* to boolean should use 'if' or 'if not'.
All Object type comparisons should use isinstance() instead of comparing types directly.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/2781

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/2781
Committed: http://github.com/openstack/quantum/commit/4572e6500ace4996f63fb12f09808346e87f9551
Submitter: Jenkins
Branch: master

commit 4572e6500ace4996f63fb12f09808346e87f9551
Author: lzyeval <email address hidden>
Date: Wed Jan 4 17:10:35 2012 +0800

    PEP8 quantum cleanup

    Fixes bug #911663

    The None, True, and False values are singletons.

    All variable *comparisons* to singletons should use 'is' or 'is not'.
    All variable *evaluations* to boolean should use 'if' or 'if not'.
    All Object type comparisons should use isinstance()
    instead of comparing types directly.

    Change-Id: Id5c797d3339d0d7015bac386088133540f0c0c9e