Update users ES index directly on save

(don't merge yet)
@czue @dannyroberts 
Waiting until tomorrow to test this out on staging, but locally it works (I see updates to users in ES even with pillowtop off).  Depends on https://github.com/dimagi/pillowtop/pull/91
Nifty!  I just added a commit doing that. https://github.com/dimagi/commcare-hq/commit/d2da092ed401e15c0ed9f459c64173915daa6137