fastannotate: pconvert paths from the server for Windows
I'm guessing that the right thing to do here is to convert the paths on the
server, but I know this is a WIP, and I don't know where that needs to happen.
I'm just trying to eliminate the malicious path warnings in the tests.
#
# Avoid interference from actual test env:
unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL