Add functional test related to bug #2850 (#2880)

## Changes
Add a functional test that proves that #2850 is already fixed

### Linked issues
Resolves #2850

### Functionality
None

### Tests
- [x] added unit tests

Co-authored-by: Eric Vergnaud <eric.vergnaud@databricks.com>

tests/unit/source_code/samples/functional/file-access/volumes.py

@@ -0,0 +1,8 @@
+df = (
+   spark.readStream.format('cloudFiles')
+   .option('cloudFiles.format', 'csv')
+   .option('cloudFiles.schemaLocation', '/Volumes/playground/test/schemas/')
+   .option('header', 'true')
+   .option('compression', 'gzip')
+   .load('/Volumes/playground/test/demo_data/')
+)