libvirt: convert firewall tests to avoid DB usage
libvirt: convert firewall tests to avoid DB usage

The test_firewall.py test suite had alot of code which created
and accessed database objects. This can all be avoided by making
more use of mock to patch out a handful of object access functions.
The test_cidr_rule_nwfilter_xml was deleted entirely since it was
never actually validating any aspect of the nwfilter execution,
so didn't add any benefits over the other test functions that
run.

Partial-bug: #1369516
Change-Id: I7172edace9e568d961fc1dc9f449cd858551bb0d

Metaswitch/calico-nova,Tehsmash/nova,sebrandon1/nova,akash1808/nova,bgxavier/nova,jianghuaw/nova,ted-gould/nova,whitepages/nova,rahulunair/nova,devendermishrajio/nova,JianyuWang/nova,eonpatapon/nova,Metaswitch/calico-nova,Stavitsky/nova,dawnpower/nova,shail2810/nova,rahulunair/nova,Yusuke1987/openstack_template,tangfeixiong/nova,BeyondTheClouds/nova,orbitfp7/nova,varunarya10/nova_test_latest,badock/nova,nikesh-mahalka/nova,affo/nova,alexandrucoman/vbox-nova-driver,jianghuaw/nova,vmturbo/nova,kimjaejoong/nova,mmnelemane/nova,CEG-FYP-OpenStack/scheduler,JianyuWang/nova,devendermishrajio/nova_test_latest,whitepages/nova,BeyondTheClouds/nova,projectcalico/calico-nova,LoHChina/nova,jeffrey4l/nova,klmitch/nova,mahak/nova,felixma/nova,fnordahl/nova,openstack/nova,takeshineshiro/nova,angdraug/nova,TwinkleChawla/nova,mikalstill/nova,JioCloud/nova_test_latest,gooddata/openstack-nova,thomasem/nova,alaski/nova,apporc/nova,Juniper/nova,alexandrucoman/vbox-nova-driver,CEG-FYP-OpenStack/scheduler,watonyweng/nova,raildo/nova,bigswitch/nova,dawnpower/nova,angdraug/nova,petrutlucian94/nova,edulramirez/nova,phenoxim/nova,edulramirez/nova,tudorvio/nova,tealover/nova,yatinkumbhare/openstack-nova,belmiromoreira/nova,mahak/nova,ted-gould/nova,raildo/nova,rajalokan/nova,hanlind/nova,joker946/nova,badock/nova,yatinkumbhare/openstack-nova,ruslanloman/nova,double12gzh/nova,j-carpentier/nova,akash1808/nova_test_latest,cernops/nova,belmiromoreira/nova,mmnelemane/nova,joker946/nova,kimjaejoong/nova,Yusuke1987/openstack_template,blueboxgroup/nova,apporc/nova,mahak/nova,vmturbo/nova,klmitch/nova,BeyondTheClouds/nova,rahulunair/nova,devendermishrajio/nova,cloudbase/nova,cernops/nova,adelina-t/nova,CloudServer/nova,JioCloud/nova,bigswitch/nova,cloudbase/nova-virtualbox,NeCTAR-RC/nova,varunarya10/nova_test_latest,Stavitsky/nova,sebrandon1/nova,MountainWei/nova,j-carpentier/nova,takeshineshiro/nova,Juniper/nova,zzicewind/nova,CloudServer/nova,watonyweng/nova,mgagne/nova,scripnichenko/nova,tealover/nova,openstack/nova,jeffrey4l/nova,tangfeixiong/nova,noironetworks/nova,alvarolopez/nova,bgxavier/nova,gooddata/openstack-nova,Francis-Liu/animated-broccoli,affo/nova,devendermishrajio/nova_test_latest,rajalokan/nova,mandeepdhami/nova,akash1808/nova,thomasem/nova,cernops/nova,jianghuaw/nova,eonpatapon/nova,zhimin711/nova,scripnichenko/nova,yosshy/nova,cloudbase/nova,iuliat/nova,cloudbase/nova-virtualbox,nikesh-mahalka/nova,CCI-MOC/nova,vmturbo/nova,zzicewind/nova,phenoxim/nova,Juniper/nova,barnsnake351/nova,cyx1231st/nova,Juniper/nova,double12gzh/nova,akash1808/nova_test_latest,maelnor/nova,cyx1231st/nova,alvarolopez/nova,Tehsmash/nova,petrutlucian94/nova,ruslanloman/nova,felixma/nova,adelina-t/nova,hanlind/nova,mandeepdhami/nova,yosshy/nova,klmitch/nova,Francis-Liu/animated-broccoli,CCI-MOC/nova,MountainWei/nova,dims/nova,alaski/nova,rajalokan/nova,mgagne/nova,fnordahl/nova,mikalstill/nova,klmitch/nova,silenceli/nova,openstack/nova,shail2810/nova,zaina/nova,isyippee/nova,isyippee/nova,gooddata/openstack-nova,rajalokan/nova,JioCloud/nova,noironetworks/nova,hanlind/nova,zhimin711/nova,gooddata/openstack-nova,barnsnake351/nova,tudorvio/nova,zaina/nova,projectcalico/calico-nova,dims/nova,jianghuaw/nova,NeCTAR-RC/nova,cloudbase/nova,vmturbo/nova,iuliat/nova,silenceli/nova,sebrandon1/nova,LoHChina/nova,TwinkleChawla/nova,maelnor/nova,orbitfp7/nova,mikalstill/nova,blueboxgroup/nova,JioCloud/nova_test_latest