arinc653: don't leak hypervisor stack contents through XEN_SYSCTL_SCHEDOP_getinfo

Note that due to XSA-77 this is not a security issue.
   
Reported-by: "栾尚聪(好风)" <shangcong.lsc@xxxxxxxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/sched_arinc653.c
+++ b/xen/common/sched_arinc653.c
@@ -705,6 +705,7 @@ a653sched_adjust_global(const struct sch
         rc = arinc653_sched_set(ops, &local_sched);
         break;
     case XEN_SYSCTL_SCHEDOP_getinfo:
+        memset(&local_sched, -1, sizeof(local_sched));
         rc = arinc653_sched_get(ops, &local_sched);
         if ( rc )
             break;