Add some more debugging to try and nail down exactly what's going on when I see traffic stalls.
Add some more debugging to try and nail down exactly what's going on when
I see traffic stalls.

It turns out that the bug isn't because the first and last frame in the
BAW is in the software queue.  It is more likely that it's because
the first frame in the BAW is still in the software queue and thus there's
no more room to allocate and do subsequent TX.

PR:		kern/166357

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase