respect accountingmax during soft hibernation
Relays now respect their AccountingMax bandwidth again. When relays entered "soft" hibernation (which typically starts when we've hit 90% of our AccountingMax), we had stopped checking whether we should enter hard hibernation. Soft hibernation refuses new connections and new circuits, but the existing circuits can continue, meaning that relays could have exceeded their configured AccountingMax. This commit rolls back some of the cpu-saving fixes, where we tried to avoid calling so many of our events while we're off the network. That's because PERIODIC_EVENT_FLAG_NEED_NET checks net_is_disabled(), which returns true even if we're only in soft hibernation. Fixes bug 32108; bugfix on 0.4.0.1-alpha.