Truncate the tcpdump expected diff to 8KB (from ~600KB).

tests/comparators/test_pcap.py

@@ -46,7 +46,7 @@ def differences(pcap1, pcap2):
 @skip_unless_tools_exist('tcpdump')
 def test_diff(differences):
     expected_diff = get_data('pcap_expected_diff')
-    assert differences[0].unified_diff == expected_diff
+    assert differences[0].unified_diff[: 2 ** 13] == expected_diff[: 2 ** 13]
 
 
 @skip_unless_tools_exist('tcpdump')