copy pcap files instead of moving (#409)

The move operation can fail in certain conditions. Copy is more robust.

testcases.py

@@ -177,7 +177,7 @@ def _inject_keylog_if_possible(self, trace: str):
             logging.debug("%s", r.stdout.decode("utf-8"))
             if r.returncode != 0:
                 return
-            shutil.move(tmp.name, trace)
+            shutil.copy(tmp.name, trace)
 
     def _client_trace(self):
         if self._cached_client_trace is None: