LOR in iflib_timer

[Eric van Gyzen]

Twice a day, my router hits an LOR in iflib_timer when it jumps to the 
"hung" label.  It's running r325049 (head 3 days ago).

lock order reversal:
  1st 0xfffffe0000f36068 igb1:tx(0):call (igb1:tx(0):call) @ 
/usr/src/sys/kern/kern_mutex.c:182
  2nd 0xfffff80003b0c150 igb1 (iflib ctx lock) @ 
/usr/src/sys/net/iflib.c:2139

This looks like it was fixed by the big rollup.  If it was fixed by a 
smallish commit, can that commit alone be merged to head?  If someone 
can point me to the commit, I'd be happy to test it.

Eric