IMPALA-1025: Use converse of data source predicate operators if expr has val before slot

Change-Id: I31790c037e2fa9af7b80c01014f7507ba5053e63
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2808
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins