ja3_fingerprint.test.py: address race condition (#11766)

ja3_fingerprint.test.py uses the Proxy Verifier client and configures it
with two sessions/connections. By default, Proxy Verifier will run the
transactions for those two connections in parallel. Generally the first
HTTP/1 session will finish before the second HTTP/2 session, but
sometimes the second session finished first. That causes the test to
fail because the gold file expects the other order. This patch addresses
this race condition issue by simply configuring the client to run the
sessions in serial rather than in parallel.

tests/gold_tests/pluginTest/ja3_fingerprint/ja3_fingerprint.test.py

@@ -134,7 +134,11 @@ def _configure_client(self, tr: 'TestRun') -> None:
         """
         name = f'client{self._client_counter}'
         p = tr.AddVerifierClientProcess(
-            name, self._replay_file, http_ports=[self._ts.Variables.port], https_ports=[self._ts.Variables.ssl_port])
+            name,
+            self._replay_file,
+            http_ports=[self._ts.Variables.port],
+            https_ports=[self._ts.Variables.ssl_port],
+            other_args='--thread-limit 1')
         JA3FingerprintTest._client_counter += 1
 
         p.StartBefore(self._dns)