Add test case for __sleep when storing to APC

Summary: This feature broke in D1417525 so just adding a unit test for the
future.

Reviewed By: @asukhachev

Differential Revision: D1478391
Use blockEndsRegion for breaksTracelet

Summary: With wholecfg there can be "tracelet" breaking things that aren't the
last block.

Reviewed By: @ottoni

Differential Revision: D1460197