Disable the vsock test.

That test has inconsistent behavior on different platforms.  See #1934 .

test/sys/test_socket.rs

@@ -2113,7 +2113,9 @@ pub fn test_recv_ipv6pktinfo() {
 }
 
 #[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg_attr(graviton, allow(unused_attributes))]
 #[cfg_attr(graviton, ignore = "Not supported by the CI environment")]
+#[ignore = "https://github.com/nix-rust/nix/issues/1934"]
 #[test]
 pub fn test_vsock() {
     use nix::errno::Errno;