mentioned in the comment the completion/callback of the triggered
send operation can happen before the call returns. If this happens and
if the pipeline depth is 0 before we triggered the send operation and
this is the last send operation of the request then the completion detection
code will decrement the pipeline depth and check it for equality to 0.
Because (0-1) != 0 the pml completion function for this request will
*not* be called.
This part 2 of the fix for ticket #246.
This commit was SVN r12292.
f3f39e003e