Clean up tempdir file used for gRPC server process to indicate success

Summary:
Feedback from https://dagster.phacility.com/D5078 also applies here - get_system_temp_directory

The part about not using IPC to indicate subprocess startup may also apply but that's a bigger fix. We could have one file to indicate success and one file to indicate failure potentially though.

Test Plan: BK + Azure

Reviewers: alangenfeld

Reviewed By: alangenfeld

Differential Revision: https://dagster.phacility.com/D5080