Race condition may cause scanners to spin with runtime filters on Avro or Sequence files

If a runtime filter arrives after per-file filtering is done, but before per-scan-range filtering, the filter may cause a header split from an Avro file to be filtered out. However, that means that BaseSequenceScanner::ProcessSplit() is not called, which would otherwise issue the remaining scan ranges in that file. This means that the exit condition for HdfsScanNode::ScannerThread() is not met, as num_unqueued_files_ and progress_ are never set to 0 or num_splits respectively. The scanner threads will therefore spin.