ALLJOYN-2181: Initialize sendTimeout member variable in the
SocketStream constructors.

Change-Id: I7ec7143df5f0c401dc36b5fc960ca5e045be12a7
ALLJOYN-2230 Lock the serial port FD to ensure exclusive access to the serial port.
Exit unit tests if serial port open failed.

Change-Id: I41af6323a2ca1012c89fc6967ea461652d379647