write_queue: Use EBADF instead of EBABDFD for portability

EBADFD is linux specific while EBADF is POSIX. Fix the build on
FreeBSD and use EBADF throughout the file.
diff --git a/src/vty/vty.c b/src/vty/vty.c
index fc86bdf..10a323f 100644
--- a/src/vty/vty.c
+++ b/src/vty/vty.c
@@ -1434,7 +1434,7 @@
 	/* Check status. */
 	if (vty->status == VTY_CLOSE) {
 		vty_close(vty);
-		return -EBADFD;
+		return -EBADF;
 	} else {
 		vty_event(VTY_WRITE, vty_sock, vty);
 		vty_event(VTY_READ, vty_sock, vty);