CLOUDSTACK-4129: select SSVM based on ImageCache data store instead of
region wide image store.
CLOUDSTACK-4204:[Object_store_refactor] Snapshot created from volume in
zone2 is copying to secondary staging storages in zone1
CLOUDSTACK-4204: return a ZoneScope in picking cache storage.
Fix simulator running
NOTE: need to use mvn -Dsimulator client jetty:run to run