[INTERNAL] removed disconnectInBandBytestreams method

This method is deprecated and the functionality is disabled.

Removed the method as it should not hurt anyone when the user
has to reconnect to the XMPP server one more time.

Change-Id: Ia54818f526f4388da9b3298806409f9bbf382e94
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/963
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>