CA-97232: Optimize host-evacuate
Case-1: When a host evacuate is in progress, ignore VMs that are shutdown
Case-2: When a host evacuate is in progress, prevent VMs from being
started on that host.

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Adding error message to datamodel

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Adding additional check in Xapi_vm_helpers.vm_can_run_on_host for VM.Start

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Merge pull request #1114 from siddharthv/CA-97232-CW

CLEARWATER: CA-97232: Optimize host-evacuate