I did some test in VIrtualBox.
Have created DNS server and DNS client.
Have configured svc:/network/dns/client:default and svc:/system/name-service/switch:default using svccfg -s options.
Everything was fine as expected, in the sense - /etc/resolv.conf and /etc/nsswitch.conf files were created and are correct but when the system restarted /etc/resolv.conf file was missing and no file, but /etc/nssswitch.conf is stay present and changes made was not there.
What's may be?