These APIs allow users to get or set time in a domain, which may come
handy if the domain has been resumed just recently and NTP is not
configured or hasn't kicked in yet and the guest is running
something time critical. In addition, NTP may refuse to re-set the clock
if the skew is too big.

In addition, new ACL attribute is introduced 'set_time'.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>