How did you upload the init script to the workspace files? Was it using the CLI? 

I suspect this could be a format issue. For example, if you upload the init script using cli, the .sh file will be considered a workspace file rather than a .sh file. For this, you must use the format option to upload the file.

 $curl -u user:pwd -H "Content-Type: application/json" -X POST -d '{"path": "/Users/<userpath>/initscript.sh","format": "AUTO","content": "==abcdefghijklmno=="}' https://adb-xxxxxxx.azuredatabricks.net/api/2.0/workspace/import --header 'Authorization: Bearer YOUR_USER_TOKEN_GENERATED_FROM_UI'