Azure `listdir` against root directory with `location` option, returns files outside `location`

[LincolnPuzey]

With the Azure backend, using listdir against the root directory and with location option configured, e.g.

# Settings
STORAGES = {
    "default": {
        "BACKEND": "storages.backends.azure_storage.AzureStorage",
        "OPTIONS": {
            ...
            "azure_container": "test-container",
            "location": "test-location",
        },
    },
}

# In your code somewhere
storages["default"].listdir("")

will return file outside the location directory.
E.g. if the files in test-container are

/test-location/some-file.txt
/something-else.txt

Both will be returned by the listdir call.

This is because location is only added when a non-empty path is provided to listdir:

django-storages/storages/backends/azure_storage.py

Lines 373 to 376 in ca89a94

	def list_all(self, path=""):
	"""Return all files for a given path"""
	if path:
	path = self._get_valid_path(path)

For comparison, S3 does not have this bug, location is always added

django-storages/storages/backends/s3.py

Lines 597 to 598 in ca89a94

	def listdir(self, name):
	path = self._normalize_name(clean_name(name))