Do not drop index build temp tables on clean shutdown

The side writes table and constraint violations table must survive clean shutdown when index builds are interrupted.

SERVER-39703 is going to add a IndexBuildBlock::deleteTemporaryTables() function and always drop the tables. This ticket must optionally call the function – e.g. not for clean shutdown when index builds are interrupted via MultiIndexBlock::abortWithoutCleanup; and also must handle the tables on startup so that we do not pile up orphaned tables – SERVER-39003 made it so that they won't be dropped on startup if they exist.