Bug 1029: Remove dead code: clustered-data-store

opendaylight/md-sal/clustered-data-store/ is dead code that is not being
built and hasn't for some time.  Its complicating keeping
versions up to date and verifying that they are up to date.

If in the future it needs to be revived it can be retrieved from
git.

Change-Id: Ie8365d5cb48e806a9d9a9fc0175478ef21277cbd
Signed-off-by: Ed Warnicke <eaw@cisco.com>