reset VM: update API.md

Add reset action for VM.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
reset VM in backend.

update mockmodel, model and controller.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
reset vm in UI

The reset in UI is first shutdown VM and then start VM.

Now UI call the reset API directly.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
add confirmation for reset a VM

Reset a VM will cause data loss without the guest OS shutdown.

We should let user confirm it.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>