Release the connection after removing it from the list

This got accidently removed in the
0d29579b

 change so this reintroduces
it.

Change-Id: I8d1eabc9f7f42852c29173f0034a9d6a2183e35a
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>
Reviewed-by: Sergey Korepanov <SergeyKorepanov@gmail.com>