Strip whitespace from worker types in Dockerfile-workers

changelog.d/14165.docker

@@ -0,0 +1 @@
+Sanitize worker list used in Docker images. Contributed by Jason Little.

docker/configure_workers_and_start.py

@@ -400,8 +400,8 @@ def generate_worker_files(
         # No workers, just the main process
         worker_types = []
     else:
-        # Split type names by comma
-        worker_types = worker_types_env.split(",")
+        # Split type names by comma, remove extra whitespace, sometimes it's there.
+        worker_types = [x.strip() for x in worker_types_env.split(",")]
 
     # Create the worker configuration directory if it doesn't already exist
     os.makedirs("/conf/workers", exist_ok=True)
@@ -420,8 +420,6 @@ def generate_worker_files(
 
     # For each worker type specified by the user, create config values
     for worker_type in worker_types:
-        worker_type = worker_type.strip()
-
         worker_config = WORKERS_CONFIG.get(worker_type)
         if worker_config:
             worker_config = worker_config.copy()