Update deps and Alpine image

- Updated deps
- Updated Alpine images to 3.16
- Removed dumb-init, not needed anymore
- Some small shellcheck tweaks on the start/healthcheck scripts

docker/amd64/Dockerfile

@@ -101,7 +101,6 @@ RUN mkdir /data \
     openssl \
     ca-certificates \
     curl \
-    dumb-init \
     libmariadb-dev-compat \
     libpq5 \
     && apt-get clean \
@@ -123,10 +122,4 @@ COPY docker/start.sh /start.sh
 
 HEALTHCHECK --interval=60s --timeout=10s CMD ["/healthcheck.sh"]
 
-# Configures the startup!
-# We should be able to remove the dumb-init now with Rocket 0.5
-# But the balenalib images have some issues with there entry.sh
-# See: https://github.com/balena-io-library/base-images/issues/735
-# Lets keep using dumb-init for now, since that is working fine.
-ENTRYPOINT ["/usr/bin/dumb-init", "--"]
 CMD ["/start.sh"]