core, restapi: move destinationVdsId to RunVmOnceParams

It should be possible to set destination VDS only when running VM in run
once mode, but nevertheless this property resided in RunVmParams instead
of RunVmOnceParams. Thus, it is moved.

Change-Id: Id6bb75da2c2030f71da26c8690a6931319f6904f
Signed-off-by: Arik Hadas <ahadas@redhat.com>