Add test for TCP over 802.3/SNAP

This admittedly is a quite esoteric combination of protocols. But - as
we do correctly support them, it seems nice to have a slightly more
complete testcase that covers this.

testing/btest/Baseline/scripts.base.protocols.snap.snap-tcp/http.log

@@ -0,0 +1,11 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+#separator \x09
+#set_separator	,
+#empty_field	(empty)
+#unset_field	-
+#path	http
+#open XXXX-XX-XX-XX-XX-XX
+#fields	ts	uid	id.orig_h	id.orig_p	id.resp_h	id.resp_p	trans_depth	method	host	uri	referrer	version	user_agent	origin	request_body_len	response_body_len	status_code	status_msg	info_code	info_msg	tags	username	password	proxied	orig_fuids	orig_filenames	orig_mime_types	resp_fuids	resp_filenames	resp_mime_types
+#types	time	string	addr	port	addr	port	count	string	string	string	string	string	string	string	count	count	count	string	count	string	set[enum]	string	string	set[string]	vector[string]	vector[string]	vector[string]	vector[string]	vector[string]	vector[string]
+XXXXXXXXXX.XXXXXX	CHhAvVGS1DHFjwGM9	192.168.1.1	12345	192.168.1.2	80	1	GET	example.com	/	-	1.1	-	-	0	12	200	OK	-	-	(empty)	-	-	-	-	-	-	FmjWkD2FgbDdTTGIGa	-	text/plain
+#close XXXX-XX-XX-XX-XX-XX

testing/btest/scripts/base/protocols/snap/snap-tcp.test

@@ -0,0 +1,3 @@
+# @TEST-EXEC: zeek -r $TRACES/snap-tcp.pcap %INPUT
+# @TEST-EXEC: btest-diff http.log
+