make deploy-app: add "wait" after pushing app before starting it
make deploy-app: add "wait" after pushing app before starting it

this is to ensure the new app's assigned service credentials have taken
effect. again, particularly a problem with new aiven-backed services,
though this is apparently still being worked on and we should be able to
remove this stopgap at some point.

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws