cros_sdk: Drop --unmount

This was associated with the --use-image feature, which we're dropping.

Leave the BAPI as a no-op.

BUG=b:266878468
TEST=./run_tests

Change-Id: If472a3d8d221ef8d3e0755c66acc7419282dad89
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4305423
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
diff --git a/api/controller/sdk_unittest.py b/api/controller/sdk_unittest.py
index 5cf8489..67333ee 100644
--- a/api/controller/sdk_unittest.py
+++ b/api/controller/sdk_unittest.py
@@ -177,6 +177,17 @@
         patch.assert_called_once_with(mock.ANY, force=True)
 
 
+class SdkUnmountTest(cros_test_lib.MockTestCase, api_config.ApiConfigMixin):
+    """SDK Unmount tests."""
+
+    def testNoop(self):
+        """Unmount is a deprecated noop."""
+        request = sdk_pb2.UnmountRequest()
+        response = sdk_pb2.UnmountResponse()
+        rc = sdk_controller.Unmount(request, response, self.api_config)
+        self.assertFalse(rc)
+
+
 class SdkUnmountPathTest(cros_test_lib.MockTestCase, api_config.ApiConfigMixin):
     """Update tests."""