nat: adding support for icmp-error msg
nat: adding support for icmp-error msg

Extending tests.

Type: test

Change-Id: I98cc1d214ead10ac53fed34a1492d9b5f37975a2
Signed-off-by: Filip Varga <a1b7c8fdf8791790807d6f2f9318dd2c069cb293@cisco.com>

FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,FDio/vpp