Fix a few compilation warnings when building in release mode

Change-Id: I4741bf7088b3723eee9d0fb0d4cdeb1dc34ef7f0
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4228
Reviewed-by: Daniel Hecht <dhecht@cloudera.com>
Tested-by: Henry Robinson <henry@cloudera.com>