tfrc: Fix loss event rate computation algo again
tfrc: Fix loss event rate computation algo again

Fix some more bugs in the loss event rate computation, also
add some optional debugging code to find future problems.

kakaroto/farstream,tieto/farstream,tieto/farstream,kakaroto/farstream,kakaroto/farstream,tieto/farstream,shadeslayer/farstream,pexip/farstream,tieto/farstream,pexip/farstream,kakaroto/farstream,pexip/farstream,shadeslayer/farstream,shadeslayer/farstream,tieto/farstream,shadeslayer/farstream,pexip/farstream