Revert "tree-wide: Don't explicity disable copy-on-write when copying images"

Let's still try to disable COW after copying. It won't do much, but
it doesn't hurt either.

See https://github.com/systemd/systemd/pull/33825/files#r1727288871.

This reverts commit 42e9288180.

src/core/exec-invoke.c

@@ -2891,6 +2891,16 @@ static int setup_ephemeral(
                 if (fd < 0)
                         return log_debug_errno(fd, "Failed to copy image %s to %s: %m",
                                                *root_image, new_root);
+
+                /* A root image might be subject to lots of random writes so let's try to disable COW on it
+                 * which tends to not perform well in combination with lots of random writes.
+                 *
+                 * Note: btrfs actually isn't impressed by us setting the flag after making the reflink'ed
+                 * copy, but we at least want to make the intention clear.
+                 */
+                r = chattr_fd(fd, FS_NOCOW_FL, FS_NOCOW_FL, NULL);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to disable copy-on-write for %s, ignoring: %m", new_root);
         } else {
                 assert(*root_directory);