test-commandserver.py: filter path separator

Was failing on Windows:

-bundle.mainreporoot=$TESTTMP/repo
+bundle.mainreporoot=$TESTTMP\repo

--HG--
branch : stable
hgweb: avoid config object race with hgwebdir (issue4326)

Turns out hgwebdir passes full repo objects to each hgweb request
instance, but with a shared baseui. We explicitly break the sharing.

--HG--
branch : stable