[FIX] session no longer auto-kill itself on session negotiation

We must ensure that we are connected to the host before we start the
session or otherwise we may trigger the error handler for missing or
broken network connections.


Change-Id: I83f08cae0f959d50e8976156429796345092c7d6
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1638
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>