Cleanup test_instance_dns
Cleanup test_instance_dns

This test was poorly named, and becomes
test_allocate_fixed_ip_instance_dns. It is also rewritten to avoid
touching the db by mocking at the nova object boundary instead of at
the db api boundary. The DNS assertions are retained from the previous
test, but the mock soup is eliminated.

Change-Id: Iaa25c451036d04d4115b85a3fa62812f3c97734e

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