Add stats to track when a pool's waiter queue is full. Reduce variable assignments
Add stats to track when a pool's waiter queue is full.
Reduce variable assignments

Signed-off-by: dleibovic <a47193dd48be59924860b05ef86ddc9a28e7bc9b@etsy.com>

vitessio/vitess,vitessio/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,mahak/vitess,vitessio/vitess