BlueNet getNeighbors() doesn't clear up list after disconnection

[jlinear]

the getNeighbors() method still returns ids after the device is disconnected.

[jtsiva]

One of the latest commits from bluenet_stack includes a mechanism to clear out the list of neighbors if an update has not been received within a certain time. This mechanism currently does not work because it throws a concurrentmodificationexception when the location manager attempts to operate on an entry when it is being updated.