security/openvpn: security fix upgrade to 2.6.11

ChangeLog: https://github.com/OpenVPN/openvpn/blob/v2.6.11/Changes.rst#overview-of-changes-in-2611

Security: 142c538e-b18f-40a1-afac-c479effadd5c
Security: CVE-2024-5594
Security: CVE-2024-28882
MFH: 2024Q2
(cherry picked from commit 97a30e46bd0b9fecac92207e719f58247a198c98)