ipadm create-if fails if /etc/ipadm/ipadm.conf doesn't exist
`ipadm create-if` fails with an unhelpful error message if /etc/ipadm/ipadm.conf does not exist. ipadm does a door_call to ipmgmtd which tries to open ipadm.conf. If the open fails, the error is propagated to ipadm. Creating the directory & making an empty file allows create-if to succeed.
The problem really is with ipmgmtd.