[INTERNAL] added synchronization to SarosNet class

The class should handle the synchronization and not the calling
classes like ConnectAction.

Change-Id: I9e556516ca1e1f4bcf49885843cdaabd62351ce9
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1251
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>