Merge from stable/10 r259381:

Merge from stable/10 r259381:

MFC r259212, r259220:

 Fix one race and one fence post error. When the TX buffer was
 completely full, we'd not complete any of the mbufs due to the fence
 post error (this creates a large leak). When this is fixed, we still
 leak, but at a much smaller rate due to a race between ateintr and
 atestart_locked as well as an asymmetry where atestart_locked is
 called from elsewhere.  Ensure that we free in-flight packets that
 have completed there as well. Also remove needless check for NULL on
 mb, checked earlier in the loop and simplify a redundant if.

Approved by:	re@ (gjb@)

git-svn-id: svn://svn.freebsd.org/base/releng/10.0@259747 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f