Reflexive ACL support on ICMP

Reflexive ACL support on ICMP

Normally session keys are generated by mirroring the packets sent.
ICMP message type should be used and inverted for the stateful ACL.

Supported ICMP messages with this patch:
 - ICMPv4: Echo/Timestamp/Information/Address Mask requests
 - ICMPv6: Echo request/Node Information Queury

The invmap & valid_new tables can be modified to make any other
ICMP messages to be reflexive ACL.

Change-Id: Ia47b08b79fe0a5b1f7a995af78de3763d275dbd9
Signed-off-by: Steve Shin <jonshin@cisco.com>