jsonrpc: VM_getStats

Align naming between API.py and schema.

Change-Id: Ia0657482b59ee0b3e943afda652e94906fe24739
Signed-off-by: pkliczewski <piotr.kliczewski@gmail.com>
Reviewed-on: http://gerrit.ovirt.org/35551
Reviewed-by: Adam Litke <alitke@redhat.com>