[INTERNAL] fix for commit 0f76be667d95a23979306c3a5f4e379f157880df

The field for the STUN port was not correctly initialized when restoring
the default values.

Change-Id: Ib553ec3f001ea536b2078371515a7cda307a15cf
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1172
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>