turbinia-client support custom turbinia config names

[wajihyassine]

What steps will reproduce the bug?

1. When running a turbinia-client request
2. Setting the environment TURBINIA_API_CONFIG_PATH to a different path
3. Command that was run: turbinia-client submit googleclouddisk --project $GCP_PROJECT --zone $GCP_ZONE --disk_name $DISK --request_id $REQUEST_ID

What is the expected behavior?

Turbinia client to parse the config without errors. I feel like we should be able to pass in a file or directory it seems to only accept directories and has to have the name turbinia_api_config.json?

What do you see instead?

TURBINIA_API_CONFIG_PATH=/home/wyassine/.turbinia_e2e_config.json
2023-11-30 19:14:22,832 ERROR turbinia - Unable to read the configuration file [Errno 20] Not a directory: '/home/wyassine/.turbinia_e2e_config.json/.turbinia_api_config.json'

Additional information

No response

[jleaniz]

The path here is intended as a directory, with the file name being static to make it easy to recognize where the configuration is stored. Removed the bug label for now. I see some value in supporting the use of a custom file name but seems to be simpler if you know it will be .turbinia_api_config.json