CLOUDSTACK-4375 VM Migration is failing from one cluster to another cluster.

Updating the fix to cover one more scenario when user directly calls API migrateVirtualMachineWithVolume.
If currentPool is accessible to destination host, skip calling allocators and move on to next volume to process.
This means if user calls migrateVirtualMachineWithVolume API where all volumes of VM are accessible on specified target host,
then API fails as there is no storage migration involved. Instead user should call migrateVirtualMachine API.

Signed-off-by: Sateesh Chodapuneedi <sateesh@apache.org>