resmoke/util/archival.py relies on deprecated and now removed thread.isAlive

Thread.isAlive was deprecated in python 3.8 and removed in 3.9, per https://bugs.python.org/issue37804

However, resmoke relies on it: https://github.com/mongodb/mongo/blob/eb2b72cf9c0269f086223d499ac9be8a270d268c/buildscripts/resmokelib/utils/archival.py#L290-L294