Add cfg.CONF.import_group for service_credentials
Add cfg.CONF.import_group for service_credentials

The cfg.CONF.service_credentials attribute is used without calling
cfg.CONF.import_group. Add calling the method in this patch.

Change-Id: I700c5ea7ae5ff3f61c28a767e5aa60db0dfb46ce
Closes-Bug: 1373753

sileht/aodh,r-mibu/ceilometer,redhat-openstack/ceilometer,openstack/ceilometer,chungg/aodh,openstack/aodh,idegtiarov/ceilometer,chungg/aodh,pkilambi/ceilometer,idegtiarov/ceilometer,cernops/ceilometer,mathslinux/ceilometer,fabian4/ceilometer,isyippee/ceilometer,ityaptin/ceilometer,mathslinux/ceilometer,r-mibu/ceilometer,isyippee/ceilometer,fabian4/ceilometer,maestro-hybrid-cloud/ceilometer,ityaptin/ceilometer,froyobin/ceilometer,pczerkas/aodh,openstack/ceilometer,Juniper/ceilometer,pczerkas/aodh,Juniper/ceilometer,sileht/aodh,pkilambi/ceilometer,froyobin/ceilometer,cernops/ceilometer,redhat-openstack/ceilometer,eayunstack/ceilometer,openstack/aodh,MisterPup/Ceilometer-Juno-Extension,m1093782566/openstack_org_ceilometer,m1093782566/openstack_org_ceilometer,eayunstack/ceilometer,maestro-hybrid-cloud/ceilometer,MisterPup/Ceilometer-Juno-Extension