Break up total network time into send and receive time.

CM has requested this and it's I think a very good way to
summarize what is taking time for each fragment. Each of
the counters in this group are non-overlapping and they
tell you what hardware resource the fragment is bottlenecked on.

Change-Id: I34a42361749c0b9c5fec39f48b588e27ca402bbb
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1472
Reviewed-by: Matthew Jacobs <mj@cloudera.com>
Tested-by: jenkins