Show the details of the added bare-metal resource

On subcommand baremetal-node-create or baremetal-add-interface,
the details of the added resource (a node or an interface) are
printed. This is useful in a script (e.g. devstack).

Some refactoring are also included.

Change-Id: I25f019f3dda33de5b49ab2c5442762283be1cf5a