CP-6826: VMs with VGPUs should not be considered agile

HA doesn't make any guarantee of PGPU availability, so we should block
any attempt to HA-protect a VM with a VGPU.

Signed-off-by: John Else <john.else@citrix.com>
Add VM agility unit test

Signed-off-by: John Else <john.else@citrix.com>