vmamd/sysinfo doesn't handle dhcp ip change

[JustinAzoff]

This presents similar to #481, but is related to the admin ip address changing. I ran into an issue when I changed the DHCP ip address for the global zone after the first boot:
{"name":"vmadmd","hostname":"srv2","pid":40182,"level":30,"msg":"spawning vnc listener for .. on 192.168.2.188","time":"2016-05-11T23:27:27.682Z","v":0}
...
Uncaught Error: listen EADDRNOTAVAIL

The root cause of this was that the sysinfo data was still returning the old IP address. I fixed things by clearing the sysinfo cache.

I think the simple fix for this is to have an /etc/dhcp/eventhook that runs sysinfo -u when a lease changes.

[rmustacc]

@melloc you may want to look at this. Though we like have similar issues with vnc and changing IPs across that. We'll have to figure out how to prioritize that.

[melloc]

@JustinAzoff I'd like to solve this by using sysevents as discussed here. There are some other things that I need to finish up before I can look into doing it, though.