postgres: resin db created by docker user

Due to recent changes in the Postgres codebase, and
rebuilds of tagged Docker images, the default `postgres`
user will no longer exist. See:
docker-library/postgres@0aff40c

Database is now created by the generated `docker` user.

Connects-to: 13
Change-type: patch
Signed-off-by: Heds Simons <[email protected]>

create-resin-db.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
 
-psql --username postgres <<-EOSQL
+psql --username docker <<-EOSQL
 	CREATE DATABASE resin;
 EOSQL