CLI: "operator root" and "operator gossip" commands are missing command file

[jrasell]

When running the nomad operator -h command, the gossip and root sections are missing their synopsis comment. This is because each of these subcommands does not have a command file, which includes this information. We should add both files with the relevant detail, so the command help output is complete.

$ nomad operator -h
Usage: nomad operator <subcommand> [options]

  Provides cluster-level tools for Nomad operators, such as interacting with
  the Raft subsystem. NOTE: Use this command with extreme caution, as improper
  use could lead to a Nomad outage and even loss of data.

  Please see the individual subcommand help for detailed usage information.

Subcommands:
    api             Query Nomad's HTTP API
    autopilot       Provides tools for modifying Autopilot configuration
    client-state    Dump the nomad client state
    debug           Build a debug archive
    gossip
    metrics         Retrieve Nomad metrics
    raft            Provides access to the Raft subsystem
    root
    scheduler       Provides access to the scheduler configuration
    snapshot        Saves and inspects snapshots of Nomad server state

[harisudarsan1]

@jrasell can I work on this?

[tgross]

@harisudarsan1 you're welcome to open a PR.