Fix active time reporting in runtime profiles.

- A few places didn't have total timer at the beginning.
- Async build thread for blocking join nodes really messed things up (sum of
  children was more than the time in the join node).

Change-Id: I9176ce37cf22f2bcebea21b117e45cce066dbc1d
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2229
Tested-by: jenkins
Reviewed-by: Nong Li <nong@cloudera.com>