Make tee sink work again

It was broken by this earlier change to NBAIO:
  > Change-Id: I5eda412648b094358f5eefc38300e9ec8a734cd3
But the code was not being compiled, so the error was not caught earlier.

Also increase the default size of per-track pipe to a reasonable value.

Change-Id: Ica05017e6c6533e1fea9df379a9b204eebed4a1f