Adding this setting avoids connection errors on some clients, when the .ovpn file is imported directly in Gnome NetworkManager.
Server logs:
Authenticate/Decrypt packet error: packet HMAC authentication failed
TLS Error: incoming packet authentication failed from ...
Client logs:
nm-openvpn: TLS Error: TLS key negotiation failed to occur within 60 seconds (check your network connectivity)
nm-openvpn: TLS Error: TLS handshake failed
NetworkManager version: 1.2.0
openvpn version: OpenVPN 2.3.10