Make test_host_filters a NoDBTestCase
Make test_host_filters a NoDBTestCase

This is the final patch in the refactoring series. This changes the
test_host_filters.py file to contain just the test of the filter handler
system and cleans up the previously database-creating TestHostFilters
class.

The entire set of host filter unit tests (around 350 of them) now run in
less than 2 seconds, down from over a 45 seconds on my workstation.

Change-Id: I2f2518a08ac3f8c6addcd4055ee4c706c4c92e8e

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