icmpv6_send: no reply to icmp error

we have this very often in the syslog of openvpn gw:

C May 9 22:53:05 hippo kernel: [15021971.775583] icmpv6_send: no reply to icmp error

we should either fix it or whitelist it in check_mk logwatch

(from redmine: created on 2014-11-07, closed on 2015-06-11)