ipsec: GCM, Anti-replay and ESN fixess

Type: fix

Several Fixes:
 1 - Anti-replay did not work with GCM becuase it overwrote the sequence
number in the ESP header. To fix i added the seq num to the per-packet
data so it is preserved
 2 - The high sequence number was not byte swapped during ESP encrypt.
 3 - openssl engine was the only one to return FAIL_DECRYPT for bad GCM
the others return BAD_HMAC. removed the former
 4 - improved tracing to show the low and high seq numbers
 5 - documented the anti-replay window checks
 6 - fixed scapy patch for ESN support for GCM
 7 - tests for anti-reply (w/ and w/o ESN) for each crypto algo

Change-Id: Id65d96b6d1d4dd821b2ab557e87468fff6d70e5b
Signed-off-by: Neale Ranns <nranns@cisco.com>