Reduce test verbosity in arp.rs

Signed-off-by: Andrew Yao <andrewyao@utexas.edu>
Co-authored-by: Himanshu Reddy <himanshureddy@utexas.edu>
Co-authored-by: Goldin Vo <goldinbaokimvo@utexas.edu>

src/vmm/src/dumbo/tcp/endpoint.rs

@@ -223,7 +223,10 @@ impl Endpoint {
                         // We have to remove the bytes up to end from receive_buf, by shifting the
                         // others to the beginning of the buffer, and updating receive_buf_left.
                         // Also, advance the rwnd edge of the inner connection.
-                        b.copy_within(end.., 0);
+                        // TODO: Maximum efficiency.
+                        for j in 0..b.len() - end {
+                            b[j] = b[j + end];
+                        }
                         self.receive_buf_left -= end;
                         // Safe to unwrap because we assert that the response buffer is small
                         // enough.
@@ -647,4 +650,4 @@ mod tests {
         let actual_response = parse_request_bytes(request_bytes, mock_callback);
         assert_eq!(actual_response, expected_response);
     }
-}
+}