Bug fix in PHJ, addresses also IMPALA-1160

In PHJ, we have to reset hash_tbl_iterator_ before probing a new batch.
Adds regression test for IMPALA-1160.

Change-Id: I608280815de2c5c1e334b7d2b4a50b12bf1d9096
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3968
Reviewed-by: Ippokratis Pandis <ipandis@cloudera.com>
Tested-by: jenkins