ufm_detach doesn't properly clean up
While iterating on some ufm related issues, I noticed that the ufm_attach(9E) was failing. The attach routine is very simple. It basically checks the command and whether or not a global dev_info is NULL. Unfortunately ufm_detach never cleans this up. The simple solution is to make sure detach NULLs this out. With this in place I've been able to see attach and detach occur in DTrace on debug bits quite frequently.