nvme: widen nvme_qpair_manual_complete_request for better errors

Make nvme_qpair_manual_complete_request take dnr as well as a
print_on_error action. Make the status word computation common between
it and nvme_qpair_manual_complete_tracker. And print the error when
we are cancelling the I/O on failure, but not when we're filtering
the I/O after we've failed. Make it private again to nvme_qpair.c.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D46049