don't grab a connection before substituting bind vars
don't grab a connection before substituting bind vars

fixes CNVS-28690

TEST PLAN:
 1) birth shard should not get trampled with useless connections in
prod

Change-Id: Ib44dcd083c92170a16dcfaad3b3c61443f97818a
Reviewed-on: https://gerrit.instructure.com/77160
Reviewed-by: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>
QA-Review: Pedro Fajardo <121b528f0c2f2e923ce3103793aca31b9a662ac4@instructure.com>
Tested-by: Jenkins
Product-Review: Ethan Vizitei <73eeb0b2f65d05a906adf3b21ee1f9f5a2aa3c1c@instructure.com>

fronteerio/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,fronteerio/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,SwinburneOnline/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,roxolan/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,fronteerio/canvas-lms,grahamb/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,HotChalk/canvas-lms,roxolan/canvas-lms,roxolan/canvas-lms,HotChalk/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,SwinburneOnline/canvas-lms,fronteerio/canvas-lms,HotChalk/canvas-lms