Fix a bug where `timeout --preserve-status` was not correctly
preserving the status code of the child process if it timed out. When
that happens, the status code of the child process is considered to be
the signal number (in this case, `SIGTERM`). The exit status of
`timeout` is then 128 plus the numeric code associated with `SIGTERM`.
To prevent clap from parsing flags for the command to run as flags for
timeout, remove the "args" positional argument, but allow to pass flags
via the "command" positional arg.
