x86/time: Update wallclock in shared info when altering domain time offset

domain_set_time_offset() udpates d->time_offset_seconds, but does not correct
the wallclock in the shared info, meaning that it is incorrect until the next
XENPF_settime hypercall from dom0 which resynchronises the wallclock for all
domains.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>

xen/arch/x86/time.c

@@ -931,6 +931,7 @@ void domain_set_time_offset(struct domain *d, int32_t time_offset_seconds)
     d->time_offset_seconds = time_offset_seconds;
     if ( is_hvm_domain(d) )
         rtc_update_clock(d);
+    update_domain_wallclock_time(d);
 }
 
 int cpu_frequency_change(u64 freq)