get rid of deprecated thread.isAlive() to use py2.6 modern form is_alive()
Summary:
Codemod to remove all thread.isAlive() since it throws a warning that is breaking some tests that monitor the output of their cli's
is_alive() was added in python 2.6 this is super safe
This is a codemod I don't care if the code supports python3, just that its python code
Test Plan: unittests
Reviewed By: cooperlees
Differential Revision: D18069520
fbshipit-source-id: 4ca4dcb541c0b0debeb194aba5d060152ad0ef0e
