test_base.py: use self._test_cwd to calculate temporary file path
test_base.py: use self._test_cwd to calculate temporary file path

Otherwise different test cases will share the same workspace.

RELNOTES: None.
PiperOrigin-RevId: 165572991

bazelbuild/bazel,meteorcloudy/bazel,ulfjack/bazel,perezd/bazel,spxtr/bazel,snnn/bazel,davidzchen/bazel,cushon/bazel,twitter-forks/bazel,perezd/bazel,snnn/bazel,cushon/bazel,akira-baruah/bazel,ulfjack/bazel,dslomov/bazel,snnn/bazel,snnn/bazel,snnn/bazel,dropbox/bazel,twitter-forks/bazel,akira-baruah/bazel,meteorcloudy/bazel,katre/bazel,davidzchen/bazel,ulfjack/bazel,bazelbuild/bazel,akira-baruah/bazel,werkt/bazel,aehlig/bazel,spxtr/bazel,akira-baruah/bazel,dropbox/bazel,dslomov/bazel,davidzchen/bazel,werkt/bazel,meteorcloudy/bazel,ulfjack/bazel,spxtr/bazel,perezd/bazel,aehlig/bazel,dslomov/bazel-windows,dslomov/bazel-windows,dropbox/bazel,dslomov/bazel-windows,aehlig/bazel,ButterflyNetwork/bazel,ButterflyNetwork/bazel,cushon/bazel,perezd/bazel,akira-baruah/bazel,davidzchen/bazel,davidzchen/bazel,ButterflyNetwork/bazel,werkt/bazel,safarmer/bazel,damienmg/bazel,werkt/bazel,dslomov/bazel,katre/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,twitter-forks/bazel,dropbox/bazel,safarmer/bazel,katre/bazel,ButterflyNetwork/bazel,katre/bazel,damienmg/bazel,aehlig/bazel,snnn/bazel,akira-baruah/bazel,dropbox/bazel,twitter-forks/bazel,bazelbuild/bazel,meteorcloudy/bazel,twitter-forks/bazel,aehlig/bazel,bazelbuild/bazel,spxtr/bazel,katre/bazel,cushon/bazel,perezd/bazel,cushon/bazel,safarmer/bazel,ulfjack/bazel,dslomov/bazel-windows,damienmg/bazel,dslomov/bazel,werkt/bazel,dslomov/bazel,aehlig/bazel,meteorcloudy/bazel,perezd/bazel,damienmg/bazel,twitter-forks/bazel,damienmg/bazel,dslomov/bazel,katre/bazel,dslomov/bazel-windows,damienmg/bazel,snnn/bazel,ulfjack/bazel,spxtr/bazel,davidzchen/bazel,meteorcloudy/bazel,twitter-forks/bazel,werkt/bazel,ulfjack/bazel,ButterflyNetwork/bazel,damienmg/bazel,safarmer/bazel,safarmer/bazel,spxtr/bazel,dslomov/bazel-windows,davidzchen/bazel,meteorcloudy/bazel,cushon/bazel,safarmer/bazel,bazelbuild/bazel,perezd/bazel,spxtr/bazel,dropbox/bazel,dslomov/bazel,aehlig/bazel