Do not replace lo0 address on Solaris

lo0 and lo0:0 are the same interface on Solaris.  Make sure
bin/tests/system/ifconfig.sh does not touch lo0:0 in order to prevent it
from changing the address of the loopback interface on Solaris.
16 jobs for 419-do-not-replace-lo0-address-on-solaris in 8 minutes and 15 seconds (queued for 2 seconds)