Recheck backfill state after we finished pipeline sync

[mattsse]

if backfillsync finished we don't do anything yet

reth/crates/engine/tree/src/tree/mod.rs

Lines 371 to 374 in 9b3a011

	FromOrchestrator::BackfillSyncFinished => {
	debug!(target: "consensus::engine", "received backfill sync finished event");
	self.is_backfill_active = false;
	}

we need to check if we can start another sync because we may have received more FCU's in the meantime