[HBASE-10538] Fix mis-use of Scan in TestSeekOptimizations

Author: daviddeng

Summary: Make endRow always exclusive.

Test Plan: TestSeekOptimizations

Reviewers: manukranthk, liyintang, rshroff

Reviewed By: rshroff

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D1180511

Task ID: 3761830

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1571789 13f79535-47bb-0310-9956-ffa450edef68