Change default cipher for server configurations to AES-GCM
At the same time, utilize the Negotiable Crypto Parameters (NCP) feature
in OpenVPN v2.4, which allows clients using the old BF-CBC default cipher
to connect without any issues.
F-27 Change request: https://fedoraproject.org/wiki/Changes/New_default_cipher_in_OpenVPN
This change was approved in the FESCO meeting 2017-08-04.
Also fix a truncated changelog entry for openvpn-2.4.3-1