fix: Use default port for healthcheck as fallback

Conduit can start without a specific port being configured.
This adjusts the healthcheck script to tolerate that state.

Closes https://gitlab.com/famedly/conduit/-/issues/222

docker/healthcheck.sh

 #!/bin/sh
 
 # If the port is not specified as env var, take it from the config file
-if [ -z ${CONDUIT_PORT} ]; then
+if [ -z "${CONDUIT_PORT}" ]; then
   CONDUIT_PORT=$(grep -m1 -o 'port\s=\s[0-9]*' conduit.toml | grep -m1 -o '[0-9]*')
 fi
 
+# If the config file also does not contain a default port, just use the default one: 6167.
+if [ -z "${CONDUIT_PORT}" ]; then
+  CONDUIT_PORT=6167
+fi
+
 # The actual health check.
 # We try to first get a response on HTTP and when that fails on HTTPS and when that fails, we exit with code 1.
 # TODO: Change this to a single wget call. Do we have a config value that we can check for that?