CLOUDSTACK-4671:ListZone API failed with Assertion error if assertion is
turned on for MS.
CLOUDSTACK-4668: Upgrade to 4.2 fails with NullPointerException when hypervisor_type is null for a cluster entry

Changes:
- Care for null value during comparing the hypervisor_type
- Do not consider removed clusters
- Method rename according to coding conventions
CLOUDSTACK-4664: [ZWPS] High delay to start a stopped VM which has ROOT/DATA volumes migrated to Second Zone wide primary Storage(More than 10 mins)

Changes:
- DeploymentPlanningManager needs to reuse the zone wide primary storage pool when VM's volume is READY
CLOUDSTACK-4651: Restarting management server when volume Snapshot is still in progress for root volume of a VM , then there is no way to restart VM since the startVM job is stuck forever since the volume is in "Snapshoting" state.

Change:
-If no volume of the VM is usable, VM cannot be deployed or started. Atleast ROOT volume should always be in usable state to start up the VM