CDH-21520: Better error message for invalid HdfsScanNode cardinality_

Change-Id: I6aaf22826d9108cd8a6e32416d636806f0631523
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4339
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins
(cherry picked from commit e993b5a95aa2c6d0c50a298c3a51e6cbd9c926a7)
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4358
Reviewed-by: Henry Robinson <henry@cloudera.com>
Tested-by: Henry Robinson <henry@cloudera.com>