Fix error messages in v3 aggregate API
Fix error messages in v3 aggregate API

Since moving error messages to HTTP responses from LOG.info()s,
the error messages has been unexpected formats like:
  "Cannot delete aggregate: %s <id>"
This patch fixes them.

Partially implements blueprint nova-v3-api

Change-Id: Iadc41ab254c1f17efdb08f23449a0bd7a94a8f6c

raildo/nova,petrutlucian94/nova_dev,leilihh/novaha,tudorvio/nova,rickerc/nova_audit,hanlind/nova,TwinkleChawla/nova,eonpatapon/nova,j-carpentier/nova,openstack/nova,mahak/nova,cyx1231st/nova,cernops/nova,virtualopensystems/nova,rickerc/nova_audit,cloudbase/nova-virtualbox,sebrandon1/nova,cloudbase/nova-virtualbox,cernops/nova,spring-week-topos/nova-week,saleemjaveds/https-github.com-openstack-nova,petrutlucian94/nova,tangfeixiong/nova,devendermishrajio/nova,spring-week-topos/nova-week,mandeepdhami/nova,cloudbase/nova,Tehsmash/nova,barnsnake351/nova,rajalokan/nova,petrutlucian94/nova,hanlind/nova,rajalokan/nova,ntt-sic/nova,apporc/nova,isyippee/nova,edulramirez/nova,vmturbo/nova,cyx1231st/nova,imsplitbit/nova,tealover/nova,projectcalico/calico-nova,scripnichenko/nova,varunarya10/nova_test_latest,tudorvio/nova,Metaswitch/calico-nova,rahulunair/nova,klmitch/nova,whitepages/nova,sebrandon1/nova,tangfeixiong/nova,gooddata/openstack-nova,nikesh-mahalka/nova,CloudServer/nova,ruslanloman/nova,mikalstill/nova,alexandrucoman/vbox-nova-driver,cloudbau/nova,maelnor/nova,devendermishrajio/nova,rrader/nova-docker-plugin,eharney/nova,cloudbase/nova,BeyondTheClouds/nova,zzicewind/nova,iuliat/nova,Juniper/nova,badock/nova,tanglei528/nova,tianweizhang/nova,LoHChina/nova,joker946/nova,varunarya10/nova_test_latest,orbitfp7/nova,rrader/nova-docker-plugin,Yusuke1987/openstack_template,cernops/nova,berrange/nova,jianghuaw/nova,ntt-sic/nova,LoHChina/nova,CiscoSystems/nova,vmturbo/nova,barnsnake351/nova,gooddata/openstack-nova,angdraug/nova,Stavitsky/nova,viggates/nova,tanglei528/nova,JioCloud/nova,nikesh-mahalka/nova,noironetworks/nova,CCI-MOC/nova,yatinkumbhare/openstack-nova,zhimin711/nova,JianyuWang/nova,CEG-FYP-OpenStack/scheduler,blueboxgroup/nova,jeffrey4l/nova,joker946/nova,bigswitch/nova,zaina/nova,scripnichenko/nova,akash1808/nova_test_latest,mahak/nova,bigswitch/nova,ted-gould/nova,alaski/nova,redhat-openstack/nova,sacharya/nova,saleemjaveds/https-github.com-openstack-nova,CloudServer/nova,vmturbo/nova,kimjaejoong/nova,luogangyi/bcec-nova,vmturbo/nova,fnordahl/nova,MountainWei/nova,klmitch/nova,alexandrucoman/vbox-nova-driver,klmitch/nova,eonpatapon/nova,j-carpentier/nova,felixma/nova,gooddata/openstack-nova,dawnpower/nova,hanlind/nova,apporc/nova,bgxavier/nova,SUSE-Cloud/nova,devendermishrajio/nova_test_latest,sebrandon1/nova,blueboxgroup/nova,mmnelemane/nova,silenceli/nova,mikalstill/nova,viggates/nova,Yuriy-Leonov/nova,watonyweng/nova,bclau/nova,projectcalico/calico-nova,tealover/nova,rajalokan/nova,yosshy/nova,thomasem/nova,iuliat/nova,watonyweng/nova,mahak/nova,isyippee/nova,devendermishrajio/nova_test_latest,eayunstack/nova,Tehsmash/nova,leilihh/nova,raildo/nova,cloudbau/nova,mikalstill/nova,Metaswitch/calico-nova,vladikr/nova_drafts,double12gzh/nova,OpenAcademy-OpenStack/nova-scheduler,alaski/nova,JioCloud/nova,openstack/nova,ruslanloman/nova,zaina/nova,BeyondTheClouds/nova,citrix-openstack-build/nova,alvarolopez/nova,whitepages/nova,shahar-stratoscale/nova,fnordahl/nova,adelina-t/nova,affo/nova,maelnor/nova,gooddata/openstack-nova,rahulunair/nova,felixma/nova,zzicewind/nova,dims/nova,klmitch/nova,mgagne/nova,phenoxim/nova,thomasem/nova,Juniper/nova,devoid/nova,berrange/nova,SUSE-Cloud/nova,cloudbase/nova,takeshineshiro/nova,NeCTAR-RC/nova,petrutlucian94/nova_dev,CCI-MOC/nova,dims/nova,shahar-stratoscale/nova,imsplitbit/nova,ewindisch/nova,OpenAcademy-OpenStack/nova-scheduler,affo/nova,belmiromoreira/nova,phenoxim/nova,shail2810/nova,eayunstack/nova,mmnelemane/nova,rajalokan/nova,Juniper/nova,akash1808/nova,devoid/nova,Stavitsky/nova,zhimin711/nova,openstack/nova,Francis-Liu/animated-broccoli,jianghuaw/nova,leilihh/novaha,eharney/nova,takeshineshiro/nova,akash1808/nova,noironetworks/nova,mandeepdhami/nova,bgxavier/nova,ewindisch/nova,Yusuke1987/openstack_template,belmiromoreira/nova,JioCloud/nova_test_latest,ted-gould/nova,rahulunair/nova,shail2810/nova,orbitfp7/nova,virtualopensystems/nova,jeffrey4l/nova,kimjaejoong/nova,citrix-openstack-build/nova,JianyuWang/nova,MountainWei/nova,akash1808/nova_test_latest,BeyondTheClouds/nova,edulramirez/nova,luogangyi/bcec-nova,adelina-t/nova,jianghuaw/nova,double12gzh/nova,alvarolopez/nova,leilihh/nova,NeCTAR-RC/nova,TieWei/nova,tianweizhang/nova,JioCloud/nova_test_latest,redhat-openstack/nova,Francis-Liu/animated-broccoli,CEG-FYP-OpenStack/scheduler,mgagne/nova,angdraug/nova,CiscoSystems/nova,dawnpower/nova,sacharya/nova,TwinkleChawla/nova,Juniper/nova,silenceli/nova,jianghuaw/nova,badock/nova,TieWei/nova,vladikr/nova_drafts,yatinkumbhare/openstack-nova,bclau/nova,yosshy/nova,Yuriy-Leonov/nova