[INTERNAL] preparation to support multiple connections

First patch to support multiple connection handling in
the network layer. The old functionality is still
supported.

Change-Id: I5048ce3ac479dfd68d1c8c81858be496cf963edd
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/949
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>