MT#56447 support log retention

... in websocket test script even if the tests succeed, for debug
purposes.

Change-Id: I54ec0b97c530e2be193c49fc887ee5b789ccf965

t/auto-daemon-tests-websocket.py

@@ -3317,7 +3317,7 @@ if __name__ == "__main__":
 
     eventloop.close()
 
-    if code == 0:
+    if code == 0 and not os.environ.get("RETAIN_LOGS"):
         os.unlink(so.name)
         os.unlink(se.name)
     else: