redis: Fix connection URL reading from config file

The previous commit (bfc981f) was missing an elif branch and therefore
the code didn't read the "url" configuration option from the config file
at all.  Fix that.

Author: suutari-ai

src/passari_workflow/redis/connection.py

@@ -30,6 +30,8 @@ def get_redis_url():
         )
     elif url and (host or port or db or password):
         raise EnvironmentError("The 'url' config for Redis is exclusive")
+    elif url:
+        return url
 
     password_part = f":{quote(password)}@" if password else ""
     port_part = f":{port}" if port else ""