lxc-to-lxd: copy rootfs by default, do not move
lxc-to-lxd: copy rootfs by default, do not move

This was hitting me by surprise when using this script. I'd argue that users
much rather expect a copy than a move. It also is more safe: If something goes
wrong users will still have their old container in place to recover.

Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

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