===DF-2404: production rdrand attach/detach leak loop===
$ vmstat -m | grep -w temp
               temp     474    337K       0    390M    5.84K
$ sysctl "kern.dfmiscgo=rdrand 20000"          (rig: verbatim rdrand.c attach/detach)
dfmisc: PRODUCTION rdrand attach/detach cycles=20000 done (M_TEMP callout
array allocated each attach; freed never)
$ vmstat -m | grep -w temp
               temp   20.0K   3.08M       0    390M    25.4K

Delta: +19,526 M_TEMP allocations in use, +2.75 MB -- one ncpus-sized
callout array (kmalloc at rdrand.c:126-127) leaked per attach/detach
cycle; rdrand_detach (rdrand.c:143-155) has no kfree.