Add comment about folsom compatibility change
Add comment about folsom compatibility change

Provide inline documentation explaining the change in
https://review.openstack.org/#/c/15778/ as requested.

Change-Id: I70c8420ddd9956d90e20449f4c7509db40b50a8e
Signed-off-by: Doug Hellmann <8c845c26a3868dadec615703cd974244eb2ac6d1@dreamhost.com>

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