ipsec: fix chained ESP

This fixes a special case when buffer chain enters decrypt node
and becomes a single buffer after decryption.

Type: fix

Change-Id: I1d4da029b952baa97400adb7173aa63fd97d916b
Signed-off-by: Filip Tehlar <ftehlar@cisco.com>
diff --git a/test/test_ipsec_esp.py b/test/test_ipsec_esp.py
index 5b057e7..cd5a88c 100644
--- a/test/test_ipsec_esp.py
+++ b/test/test_ipsec_esp.py
@@ -509,9 +509,10 @@
                            count=NUM_PKTS)
 
         LARGE_PKT_SZ = [
+            1970,  # results in 2 chained buffers entering decrypt node
+                   # but leaving as simple buffer due to ICV removal (tra4)
             4010,  # ICV ends up splitted accross 2 buffers in esp_decrypt
                    # for transport4; transport6 takes normal path
-
             4020,  # same as above but tra4 and tra6 are switched
         ]
         if self.engine in engines_supporting_chain_bufs: