Refactor: libpacemaker: Pass NULL input in pcmk__simulate()

...to pcmk__schedule_actions().

When pcmkschedule_actions() is called, cluster_status() has already
set the pcmksched_have_status flag. So unpack_cib() doesn't reset the
scheduler or set scheduler->input; it only sets the given flags.

There's also no longer any reason to pass flags, since
pcmk__schedule_actions() is no longer resetting the scheduler. The
existing flags will be kept.

pcmk__schedule_actions() has a use-after-free bug if its cib argument is
the same as the current scheduler->input (or if it's an ancestor or
descendant). This is another step toward dropping that argument.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>