test: ignore a ConnectionResetError during our dispatch

If our server disconnects us with data still in the pipe we never picked
up on that data causing heisenbugs depending on whether we read things
(esp. the "disconnected" event) fast enough or not.

Part-of: <https://gitlab.freedesktop.org/libinput/libei/-/merge_requests/317>

test/test_protocol.py

@@ -233,7 +233,7 @@ class Ei:
             while data:
                 self._data += data
                 data = self.sock.recv(1024)
-        except BlockingIOError:
+        except (BlockingIOError, ConnectionResetError):
             pass
         return self.data