xen/sched: don't call sync_vcpu_execstate() in sched_unit_migrate_finish()

xen/sched: don't call sync_vcpu_execstate() in sched_unit_migrate_finish()

With support of core scheduling sched_unit_migrate_finish() gained a
call of sync_vcpu_execstate() as it was believed to be called as a
result of vcpu migration in any case.

In case of migrating a vcpu away from a physical cpu for a short period
of time but without ever being scheduled on the selected new cpu, this
might not be true so drop the call and let the lazy state syncing do its
job.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Dario Faggioli <dfaggioli@suse.com>