Default command line argument `in_pod` was set to True, but this breaks
the compose file for users who want to use `--userns` argument. This
commit sets default `in_pod` value to None, and later resolves whether
to create a pod by checking compose file, as new argument in compose
file x-podman is now available. Now it is convenient for users to pass
custom `in_pod` value (True or False) as a compose file argument when
command line value of `in_pod` is not provided.
Signed-off-by: Monika Kairaityte <monika@kibit.lt>
