Improve pg_ctl's message for shutdown after recovery.

Improve pg_ctl's message for shutdown after recovery.

If pg_ctl tries to start the postmaster, but the postmaster shuts down
because it completed a point-in-time recovery, pg_ctl used to report
a message that indicated a failure.  It's not really a failure, so
instead say "server shut down because of recovery target settings".

Zhao Junwang, Crisp Lee, Laurenz Albe

Discussion: https://postgr.es/m/CAGHPtV7GttPZ-HvxZuYRy70jLGQMEm5=LQc4fKGa=J74m2VZbg@mail.gmail.com