Raise stevedore requirement to 0.7
Raise stevedore requirement to 0.7

Nova already requires 0.7, so we can easily consolidate on
a newer release.

Change-Id: If983ea0c987eb00d66a602459e37805d8ef0bfe4

cernops/ceilometer,JioCloud/ceilometer,rackerlabs/instrumented-ceilometer,rackerlabs/instrumented-ceilometer,mathslinux/ceilometer,m1093782566/openstack_org_ceilometer,idegtiarov/ceilometer,ityaptin/ceilometer,shootstar/ctest,chungg/aodh,chungg/aodh,sileht/aodh,idegtiarov/ceilometer,ityaptin/ceilometer,eayunstack/ceilometer,maestro-hybrid-cloud/ceilometer,rickerc/ceilometer_audit,rackerlabs/instrumented-ceilometer,isyippee/ceilometer,tanglei528/ceilometer,rickerc/ceilometer_audit,maestro-hybrid-cloud/ceilometer,pkilambi/ceilometer,citrix-openstack-build/ceilometer,citrix-openstack-build/ceilometer,JioCloud/ceilometer,dreamhost/ceilometer,luogangyi/Ceilometer-oVirt,tanglei528/ceilometer,luogangyi/Ceilometer-oVirt,openstack/aodh,NeCTAR-RC/ceilometer,MisterPup/Ceilometer-Juno-Extension,pkilambi/ceilometer,citrix-openstack-build/ceilometer,cernops/ceilometer,redhat-openstack/ceilometer,JioCloud/ceilometer,isyippee/ceilometer,pczerkas/aodh,openstack/ceilometer,NeCTAR-RC/ceilometer,mathslinux/ceilometer,froyobin/ceilometer,tanglei528/ceilometer,openstack/aodh,fabian4/ceilometer,shootstar/ctest,r-mibu/ceilometer,MisterPup/Ceilometer-Juno-Extension,rickerc/ceilometer_audit,froyobin/ceilometer,NeCTAR-RC/ceilometer,m1093782566/openstack_org_ceilometer,Juniper/ceilometer,pczerkas/aodh,eayunstack/ceilometer,r-mibu/ceilometer,openstack/ceilometer,Juniper/ceilometer,dreamhost/ceilometer,redhat-openstack/ceilometer,sileht/aodh,fabian4/ceilometer