Fix ironic node state comparison
Fix ironic node state comparison

Using "is not" is an identity comparison and doesn't compare actual
values. If NOSTATE were to be changed from None to a string, this
would likely break.

Change-Id: I96706e0a3a39971c3661210dbd13a8bc990a8933
Closes-Bug: #1315050

naototty/vagrant-lxc-ironic,hpproliant/ironic,bacaldwell/ironic,SauloAislan/ironic,dims/ironic,faizan-barmawer/openstack_ironic,ramineni/myironic,Tehsmash/ironic,NaohiroTamura/ironic,froyobin/ironic,devananda/ironic,redhat-openstack/ironic,SauloAislan/ironic,NaohiroTamura/ironic,openstack/ironic,naterh/ironic,ionutbalutoiu/ironic,dims/ironic,pshchelo/ironic,rdo-management/ironic,supermari0/ironic,rackerlabs/ironic,Tan0/ironic,openstack/ironic,ionutbalutoiu/ironic,naototty/vagrant-lxc-ironic,pshchelo/ironic,bacaldwell/ironic,debayanray/ironic_backup