Should any dcuid that is not classified as a MYRINET_DCU (normal dcu) be handled by the daqd?

See issue #95 (closed). The crash was due to dcuid 4 being used, which took it out of the regular code path that is guarded by IS_MYRINET_DCU(...).

Are there any cases where we handle special dcus anymore. If not the daqd should crash with an error message saying the dcuid is bad.