jailer: commented for using  in netns
jailer: commented for using  in netns

author written a TODO to check why EBADFD is faced while using
`as_raw_fd` but not in `into_raw_fd`. added a comment to clarify
that.

Signed-off-by: karthik.n <e4e36e275c88378e927f245cdd9c5374c766fe88@zohocorp.com>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker