By default, clap  does not allow to provide the same argument more than
once, for instance if we call:
`virtiofsd --xattr --xattr ...`

it will show the following error:
`error: The argument '--xattr' was provided more than once, but cannot
be used multiple times`

This is not compatible with the C version, and also it breaks the use of
annotations in Kata:
`io.katacontainers.config.hypervisor.virtio_fs_extra_args`
it appends the extra arguments to the default ones used by Kata,
failing to start the pod if a duplicated argument is provided, for
instance `--thread-pool-size=`.