Fix: libcluster: never autoreap from remote peer cache

This commit prevents autoreaping of the remote peer cache in
crm_update_peer_state_iter(). At this point, a remote peer's state
is always member, so this has no effect on behavior yet. But once
crm_remote_peer_cache_refresh() starts setting remote peer state,
reaping will be handled there, so we don't want it to happen here.