jsonrpc: VM_setCpuTunePeriod

Align naming between API.py and schema.

Change-Id: Iac8159c951bb9b85914a51e78e9678c2918097b6
Signed-off-by: pkliczewski <piotr.kliczewski@gmail.com>
Reviewed-on: http://gerrit.ovirt.org/35552
Reviewed-by: Oved Ourfali <oourfali@redhat.com>
Reviewed-by: Martin Sivák <msivak@redhat.com>
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>