Avoid running bogus tests with Fastmail

The fix that disabled VTODO tests accidentally ran all other tests twice
for this storage.

This wasn't picked up earlier since Fastmail is not currently running on
CI.

Author: Hugo Osvaldo Barrera

tests/storage/servers/fastmail/__init__.py

@@ -5,11 +5,12 @@
 
 class ServerMixin:
     @pytest.fixture
-    def get_storage_args(self, item_type, slow_create_collection, aio_connector):
-        if item_type == "VTODO":
-            # Fastmail has non-standard support for TODOs
-            # See https://github.com/pimutils/vdirsyncer/issues/824
-            pytest.skip("Fastmail has non-standard VTODO support.")
+    def get_storage_args(self, slow_create_collection, aio_connector, request):
+        if "item_type" in request.fixturenames:
+            if request.getfixturevalue("item_type") == "VTODO":
+                # Fastmail has non-standard support for TODOs
+                # See https://github.com/pimutils/vdirsyncer/issues/824
+                pytest.skip("Fastmail has non-standard VTODO support.")
 
         async def inner(collection="test"):
             args = {