xen: fix timer bug found by updated test

Only 'tsc' timer allows set mode and track is valid only for 'rtc' and
'platform' timers.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/xenconfig/xen_common.c

@@ -553,6 +553,8 @@ xenParseCPUFeatures(virConfPtr conf, virDomainDefPtr def)
             timer->name = VIR_DOMAIN_TIMER_NAME_HPET;
             timer->present = val;
             timer->tickpolicy = -1;
+            timer->mode = -1;
+            timer->track = -1;
 
             def->clock.ntimers = 1;
             def->clock.timers[0] = timer;

src/xenconfig/xen_sxpr.c

@@ -1262,6 +1262,8 @@ xenParseSxpr(const struct sexpr *root,
             timer->name = VIR_DOMAIN_TIMER_NAME_HPET;
             timer->present = sexpr_int(root, "domain/image/hvm/hpet");
             timer->tickpolicy = -1;
+            timer->mode = -1;
+            timer->track = -1;
 
             def->clock.ntimers = 1;
             def->clock.timers[0] = timer;