charon-nm: Set DPD/close action to restart and enable indefinite keying tries

charon-nm: Set DPD/close action to restart and enable indefinite keying tries

We don't track CHILD_SA down events anymore and rely on NM's initial timeout
to let the user know if the connection failed initially.  So we also don't
have to explicitly differentiate between initial connection failures and
later ones like we do an Android.  Also, with the default retransmission
settings, there will only be one keying try as NM's timeout is lower than
the combined retransmission timeout of 165s.

There is no visual indicator while the connection is reestablished later.

Fixes #3300.