MB-2690 - don't assert on STATS error

Change-Id: I09987384feb3a04f212dcb206d9668b44703e749
Reviewed-on: http://review.membase.org/3579
Tested-by: Dustin Sallings <dustin@spy.net>
Reviewed-by: Dustin Sallings <dustin@spy.net>

cproxy_protocol_a2b.c

@@ -976,10 +976,10 @@ void a2b_process_downstream_response(conn *c) {
             item_remove(it);
             conn_set_state(c, conn_new_cmd);
         } else {
-            // Handle the stats terminator.
+            // Handle the stats terminator, which might have an error or
+            // non-empty bodylen, for some implementations of memcached protocol.
             //
             assert(it == NULL);
-            assert(bodylen == 0);
             conn_set_state(c, conn_pause);
         }
         break;