ip6: during icmp to icmp6 translation truncate error messages
ip6: during icmp to icmp6 translation truncate error messages

All translated ICMPv6 packets that exceed the minimal IPv6 MTU get
truncated but according to RFC 4443 2.4 only ICMPv6 error messages
(type < 128) need to be truncated.

With this commit, truncate only ICMPv6 error messages.

Type: fix

Change-Id: Ic455352de2ff4ff6aa3421b46a2a54923f2d3f80
Signed-off-by: Alexander Chernavin <005bca4307cd9b117df45182181fee477edfa768@netgate.com>

FDio/vpp,chrisy/vpp,chrisy/vpp,vpp-dev/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,vpp-dev/vpp,FDio/vpp,vpp-dev/vpp,chrisy/vpp,FDio/vpp,vpp-dev/vpp,vpp-dev/vpp,FDio/vpp,chrisy/vpp,vpp-dev/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,vpp-dev/vpp,FDio/vpp,FDio/vpp