The 'force' option provided with the stopVirtualMachine API command is
often assumed to be a hard shutdown sent to the hypervisor, when in fact
it is for CloudStacks' internal use. CloudStack should be able to send
the 'hard' power-off request to the hosts.
When forced parameter on the stopVM API is true, power off (hard shutdown)
a VM. This uses initial changes from #1635 to pass the forced parameter
to hypervisor plugin via the StopCommand, and fixes force stop (poweroff)
handling for KVM, VMware and XenServer.
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>