pm-utils: use `qvm-sync-clock --force` instead of manual qvm-run

After suspend VMs clocks are desynchronized in most cases (because VMs
were paused). Since directly after suspent there may be no network
access, normal `qvm-sync-clock` call isn't good (it aborts if NTP call
fails). But with new `qvm-sync-clock --force` switch, it sync VMs even
if NTP is unreachable.

QubesOS/qubes-issues#1728

pm-utils/01qubes-sync-vms-clock

@@ -2,13 +2,8 @@
 
 sync_qubes_vms_wallclock()
 {
-    # Sync all VMs based on dom0 clock
-    DATE=$(date)
-    echo
-    echo "Syncing VMs clock to: $DATE"
-    qvm-run --all -u root --localcmd="date -u -Iseconds" "qubes.SetDateTime dom0"
-    # Then try to sync from the network
-    /usr/bin/qvm-sync-clock &
+    # Sync all VMs (based on dom0 clock if network time sync fails)
+    /usr/bin/qvm-sync-clock --force &
 }
 
 case "$1" in