No DB connection from docker

*This issue was originally created by [**@fierg**](https://github.com/fierg) at .*

### Background information

- **Dendrite version or git SHA**: Dendrite release 0.11.1 (image)
- **SQLite3 or Postgres?**: Postgres
- **Running in Docker?**: Docker
- **`go version`**: go1.19.6 linux/amd64

- **Client used (if applicable)**:

### Description

- **What** is the problem:
Cannot connect to the database in docker
- **Who** is affected: Just Me
- **How** is this bug manifesting: (monolith_1 | time="2023-02-23T08:08:08.295379567Z" level=panic msg="Failed to set up global database connections" error="failed to find maximum connections: dial tcp 127.0.0.1:5432: connect: connection refused")
- **When** did this first appear: right after the first installation

### Steps to reproduce

- pull repo
- generate passwords, fill dedrite.yaml
- start docker-compose

The database is up and running, i can access it via pgAdmin, but the dendrite container cannot.

Start with the docker-compose setup and dendrite.yaml, then compare the configured PostgreSQL host with the container log showing a connection attempt to 127.0.0.1:5432. Reproduce the first-install startup and verify that the Dendrite container can connect to the running database; done means the global database connections initialize without the panic.

Written by the indexing model from the issue text.