When the firmware tells us a loop id is already in use, add the device

When the firmware tells us a loop id is already in use, add the device
there to our port lists, then find the next available loop id and carry on
rather than restarting.  This way, we're less likely to get stuck looping
when the firmware behaves inconsistently.  We also don't need to treat domain
controller logins specially.

additional complications discovered by deraadt@