Fix issue with using geospatial index spec as sort spec.

Currently this passes because `this.indexExists` is undefined
within the context of the worker threads, causing it to always
call sort() instead of hint().
Make changes to $config.data in setup visible to worker threads.
Drop collections and databases in teardown of mapReduce workloads.
Rename fsm_workload_helpers/ to fsm_workload_modifiers.
Add helpers for dropping collections and databases.
Use drop_utils.js helpers in other workloads.

Also changed to specify full pattern.
Fix issue with regular expressions.

Need to use '\\d' instead of '\d'. Also gave names to the overridden
functions.