I don't know how to stop the testing of the ethernet connections, but some years back when I worked on E10Ks with many NIC cards I created a RJ45 loopback. I would simply plug it in and move it as needed.
http://www.juniper.net/techpubs/software/nog/nog-interfaces/html/fe-ge-loopback 25.html
Actually, I found the solution by myself.
I have commented in a couple of lines in the /Solaris_10/Tools/Boot/sbin/install-discovery script on my jumpstart server.
The idea is to get rid of "ifconfig $i auto-revarp"
This command wastes a lot of time getting the IP address from the network interfaces which are not even connected into the network
They had to check the link state before doing this command.