illumos gate

For a DHCP global zone, identity-node (svc:/system/identity:node) will use DHCP Hostname if returned. identity-node does nothing for an exclusive-IP, DHCP, non-global zone, but it could do easily the same -- but ensuring the previously-existing, non-global zone fallback to `uname -n` after /etc/nodename for DHCP as well.

Also, identity-node only tries once to fetch Hostname from dhcpagent (dhcpinfo), which generally works for a global zone. For fast-booting non-global zones, there needs to be a few seconds allowance — so update to retry checks for a short interval. (The repeating query will be OK as well for a global zone).