BUG-1074: add javadoc for QueueKeeper

- added javadoc for QueueKeeper and QueueKeeperImpl

Change-Id: I5cf4d5c2798766435985bb9a93c45b07e18d4d8b
Signed-off-by: Michal Rehak <mirehak@cisco.com>
Merge "BUG-1074: add javadoc for QueueKeeper"