[STF] connect concurrently

This should speed up the initialization process.

Change-Id: I5e6da3b28b61304e85f32de51ec6dfb86d9212c3
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1903
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>