Bug 1029: Remove dead code: clustersession

opendaylight/samples/clustersession/ 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 it needs to be revived in the future it can be retrieved
from git.

Change-Id: I59c0e989749eb2b69eb6b34b1a59aca21c053d26
Signed-off-by: Ed Warnicke <eaw@cisco.com>