Ignore openvpn logwatch warnings

LOG /var/log/syslog  CRITICAL CRIT - 3 CRIT messages (Last worst: "Mar 5 11:15:48 seahorse ovpn-udp_config[2420]: 0.0.0.0:55723 TLS_ERROR: BIO read tls_read_plaintext error: error:140890C7:SSL routines:SSL3_GET_CLIENT_CERTIFICATE:peer did not return a certificate")

(from redmine: created on 2015-04-15, closed on 2015-07-07)