Fix DB access by FormatMappingTestCase
Fix DB access by FormatMappingTestCase

Change I682a377d769312e8f37f874aa4548665b3b52ed3 made this test
inherit from NoDBTestCase. However, this test does access the db if
ec2utils.get_int_id_from_snapshot_uuid() can't return a value from its
memo cache. That is, it was only passing due to fortunate test
ordering which populated this cache in a previous test. If you ran the
test isolated, it failed.

This change mocks ec2utils.id_to_ec2_snap_id to return expected values
without touching the db.

Change-Id: I9e44f93dba5d56bf8c3dd3fda28a9b54eb95507f

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