perf-tags: fix clear_cache_fnodes to actually clear that cache The function was not doing it what it advertise for a long time. So we fix it and we add a way for the perf extensions to detect broken version.

perf-tags: fix the --clear-fnode-cache-rev code It seems like this code never run?

tests: do not fail tests in a state with uncommitted .py file removal The problem is that [hg locate] lists removed files too. We use [hg files] instead because that does not list removed files.