Fix two mutually cancelling bugs.

* mandos (rfc3339_duration_to_delta): Set "token_duration" to be a
                                      token (and not a tuple) by
                                      removing the final comma.
                                      Construct the needed tuple later
                                      when initializing the
                                      "followers" variable.
* mandos-ctl (rfc3339_duration_to_delta): - '' -