(CFACT-86) Solaris: fix network address

Previously, the networking resolver did not resolve the network address
correctly. This patch gets the network address from the ipaddress and the
netmask correctly.
I see, we're modifying `addr` in a call to `ioctl`.  It'd probably be best if we declared a local `lifreq` and pass the address of that instead of modifying the caller's data (the `ioctl` call is not const-correct).