qvm-sync-clock running in background is killed as soon as
qubes-suspend.service is terminated.
Additionally restore --verbose option, which was the case (implicitly)
in previous qvm-run based code.
FixesQubesOS/qubes-issues#1795
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
