6LowPan: Change how the destination node address is handled in the start...

6LowPan:  Change how the destination node address is handled in the start endpoint configuration.   When the star endpoint sent the IPv6 destination address, the HC06 compression logic elided the address -- meaning that it could be reconstructed by the recipient based on the receiver's assigned short address.  However, when intercepted by the hub, the uncompressed address does not know the short address of the recipient and instead uses the short address of the hub.  This means two things:  (1) it looks like  the hub address is the destination address, and (2) the uncompressed UDP packet has a bad checksum.  This change assures that the destination IPv6 address is not elided in the case of the star endpoint configuration.