ffs_truncate3 panics

[Rick Macklem]

Just fyi, I have committed r337962 to head, which stops the pNFS service
from creating non-zero length empty files.
Since these files were the ones causing the "ffs_truncate3" panics, the panics
should no longer occur.

I will take a closer look at some point to see if I can spot why the panics()
occur and can easily revert this patch on my test setup if others have
suggested patches to try related to this.

Thanks for your help with this, rick