wait-for-it script was left out from the postgres directory after
the update to the Dockerfile that relies on it. Adding the script
in that directory so our Dockerfile builds correctly.
Change-Id: I1c445937ff809877a7063a37eb5b1052e3ae5af5
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/217588
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Tested-by: Jenkins
Reviewed-by: Derek Bender <djbender@instructure.com>
QA-Review: James Butters <jbutters@instructure.com>
Product-Review: James Butters <jbutters@instructure.com>