Use btm prepared statement cache (See #11033)

Suggestion on the list was that the time to remove
the 1K or 10K uncached prepared statements from the
single collection was causing the long hangs. Here,
we've moved up to btm 2.1.3 and set the prepared
statement cache to 10 by default. (Note: for some
DBs this will require more active connections)
Merge pull request #1243 from joshmoore/11033-delete-times

Use btm prepared statement cache (See #11033)