[INTERNAL] omit the sending of the session id in the TransferDescription

The sessionID in the TransferDescription is only used by the
StreamServiceManager who is setting this value by itself.

Change-Id: If1c1e3680ba568305cf7eeed7842fc9942b2f409
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/966
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>