Fix `error mounting "/etc/hosts" to rootfs at "/etc/hosts": mount
/etc/hosts:/etc/hosts (via /proc/self/fd/6), flags: 0x5021: operation
not permitted`.
This error was introduced in 7d08d84b03
(`dockerd-rootless.sh: set rootlesskit --state-dir=DIR`) that changed
the filesystem of the state dir from /tmp to /run (in a typical setup).
Fix issue 47248
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>