[HBASE-8185] ReadOnlyStore should throw when it finds inconsistent region directories.

Author: manukranthk

Summary: ReadOnlyStore should throw an exception when it finds that the region directory is not found. Currently it creates a new directory with that name and continues, which is a valid behavior for a Store but not a valid behavior for ReadOnlyStore.

Test Plan: Unit Testing

Reviewers: liyintang, rshroff, aaiyer

Reviewed By: aaiyer

CC: hbase-eng@

Differential Revision: https://phabricator.fb.com/D829510

Task ID: 2446974

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.89-fb@1488343 13f79535-47bb-0310-9956-ffa450edef68