fix a mistake intro-ed in D5826, see  - the tests didnt catch it because the the [ get_output_manager | https://sourcegraph.com/github.com/dagster-io/dagster/-/blob/python_modules/dagster/dagster/core/execution/context/system.py#L325:17 ] defaults to IntermediateStorageAdapter(mem_intermediate_storage) if the user doesn't specify neither intermediate storage or object manager.
so this diff switches the logic to check "is default intermediate storage" instead of "is default object manager" in the adapting
logic - so we would be using mem_object_manager as the default rather than the adapted mem intermediate storage
however, because object managers are resources, the default mem_object_manager won't work for things like `result.result_for_solid`. it's because 
`output_value` will reconstruct the pipeline context, where resources get re-initiated, which means we would lose the in-memory values in the mem_object_manager as the object_manager in output_value is going to be a brand new instance of the `InMemoryObjectManager`.