IMPALA-1384: Fix show table stats test on exhaustive test run

Change-Id: I2f1033bc078906ce72a19099f214ab4e3cd9a936
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4824
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins
(cherry picked from commit 0ead02755b6a65d408bed59df810114e26c0c397)
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4830
Reviewed-by: Henry Robinson <henry@cloudera.com>