Remove unused instance_group_metadata_* DB APIs
Remove unused instance_group_metadata_* DB APIs

Apparently these were never used and added awhile
ago with commit 501ff418df4. Since they aren't used
anywhere (not even tested), let's remove them.

Change-Id: I2b67a75b90b78ec82917936083a88d3e394bbb27

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