Test fix for external_jdbc_auth.q

The external_jdbc_auth.q test fails due to the following errors :
java.lang.AssertionError:
Client Execution succeeded but contained differences (error code = 1) after executing external_jdbc_auth.q
220,221c220,221
< 20 20 20.0 20.0
< 20 20 20.0 20.0
—
> 20 20 20.0 20.0 20
> 20 20 20.0 20.0 20
 
This test was newly added in https://issues.apache.org/jira/browse/HIVE-20651 but the test has continuously failed on branch-3. Needs a fix. No other change had been committed to this test after this ticket. Since the ticket was merged in branch-3 without validating the test, fixing it now.