[Epoch Sync] Epoch sync should always do something if we're in SyncStatus::EpochSync

[robin-near]

Description

Currently we check three conditions before doing epoch sync: config not disabled, header head at genesis, highest height is far ahead enough. In weird cases it might happen that some of these are no longer true after they were initially true. We should make sure that if we're already in SyncStatus::EpochSync but these conditions became no longer all true, we should exit SyncStatus::EpochSync, or else the node would be stuck on that state, as nothing else can make progress.