Changing the way how the bare-metal cluster works

In the current implementation, the bare-metal mode cluster runs in the foreground, so it supports:
- `delete`: does not support, but disrupting the foreground process will clean its metadata
- `list`: does not support
- `get`: retrieve the current cluster profile

It occurs to me that some users may wish gtctl will not perform `delete` while disrupting the foreground process (ref #155), so I propose a new way for bare-metal mode cluster to work. Since it no longer delete the metadata when the foreground process is shutting up, so:
- `delete`: will do as just #155 points out
- `list`: will list all the cluster metadata in localhost
- `get`: will perform get operation on specific cluster