Help text for fdbcli suspend command is unclear

The help text for the suspend command in fdbcli does not really describe what it means to suspend a process. It also says:

```
For each IP:port pair in , attempt to suspend the processes for the
specified SECONDS after which the process will die.
```

This I think is exposing the implementation details in a somewhat confusing way. The `SECONDS` parameter is meant to determine how long the process will be suspended, and possibly killing the process is how we actually unsuspend it, but this assumes some knowledge of what's happening under the hood that isn't explained else where in this text.