[IMP] 11.0-13.0: Wait for PostgreSQL before starting Odoo

In some situations, like when a docker compose file use a data volume
to persist postgresql databases, the Odoo server starts and tries to
connect to database server before the postgresql server is ready.

In such a case, the Odoo containers fails to start.

With this commit, the wait-for-it script is used to wait for the
database server service to be ready before starting Odoo.

This script is available as a Debian package.

Closes #258, closes #259

12.0/Dockerfile

@@ -13,6 +13,7 @@ RUN set -x; \
         && apt-get install -y --no-install-recommends \
             ca-certificates \
             curl \
+            wait-for-it \
             dirmngr \
             fonts-noto-cjk \
             gnupg \