Helm should only set --controller_config_file conditionally

[jlewi]

Our helm chart currently always sets controller_config_file

This causes problems if the config_file doesn't actually exist which is the case if the user doesn't specify the cloud flag when installing the helm chart. I suspect this is the problem in #149 and #173.

We should modify the helm chart so that controller_config_file is only set if a config map is specified.

[DjangoPeng]

How about setting an empty configmap by default? Please take a look at the patch. If we prepare the empty configmap, it's easy for users to specify something individual based on the updated config.yaml. If they don't specify anything, helm install successfully as well.

[jlewi]

@DjangoPeng can you review #176 please? What's the advantage of providing an empty config map as opposed to just not providing a config map and setting the flags accordingly.

With #176 if a user wants to specify a custom map then they can do something like this

 helm install ./tf-job-operator-chart --dry-run --debug --set config.configmap=custom_map

and specify the name of whatever config map they want to use. I also added an option to override the default name for the file used.