Add a missing sys import in test/distributed/rpc/test_tensorpipe_agent.py (#54925)
Summary:
`sys` is used a couple of lines below.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54925
Reviewed By: agolynski
Differential Revision: D27434941
Pulled By: H-Huang
fbshipit-source-id: b03c9373ee77e7a158964f619b29967fa55226d0
