nat: add ipfix rate-limiter for nat44-ed, nat44-ei and nat64

This prevents ipfix flood with the repeating events and allows
to enable nat64 max_session and max_bibs events. Also fix wrong
endian for det44 and nat64 ipfix tests, now should be fine with
extended tests enabled.
Max session per user event @ nat44-ei requires more precise rate
limiter per user address, probably with sparse vec, not handled.

Type: improvement
Signed-off-by: Vladislav Grishenko <themiron@yandex-team.ru>
Change-Id: Ib20cc1ee3f81e7acc88a415fe83b4e2deae2a836
diff --git a/test/test_det44.py b/test/test_det44.py
index ecd57a6..ede8098 100644
--- a/test/test_det44.py
+++ b/test/test_det44.py
@@ -98,9 +98,9 @@
         # natEvent
         self.assertEqual(scapy.compat.orb(record[230]), 13)
         # natQuotaExceededEvent
-        self.assertEqual(struct.pack("I", 3), record[466])
+        self.assertEqual(struct.pack("!I", 3), record[466])
         # maxEntriesPerUser
-        self.assertEqual(struct.pack("I", limit), record[473])
+        self.assertEqual(struct.pack("!I", limit), record[473])
         # sourceIPv4Address
         self.assertEqual(socket.inet_pton(socket.AF_INET, src_addr), record[8])
 
@@ -724,7 +724,7 @@
 
         # verify IPFIX logging
         self.vapi.ipfix_flush()
-        capture = self.pg2.get_capture(2)
+        capture = self.pg2.get_capture(7)
         ipfix = IPFIXDecoder()
         # first load template
         for p in capture: