tests/test-empty-dir.t

logexchange: convert paths to unix when detecting the active path

This fixes the problem in the tests[1] where Windows was showing the whole path
as the remotename for local repositories.

Somebody with a better understanding of this extension should probably take a
deeper look.  There may be other cases that need to be converted- specifically
the `elif not instance` and the missing `else` cases in activepath().  I also
noticed when adding debug prints that the absolute path is stored in the file,
probably not normalized.  (It's wrapped up in $TESTTMP.)

[1] https://buildbot.mercurial-scm.org/builders/Win7%20x86_64%20hg%20tests/builds/1042/steps/run-tests.py%20%28python%202.7.13%29/logs/stdio

  $ hg init

  $ echo 123 > a
  $ hg add a
  $ hg commit -m "first" a

  $ mkdir sub
  $ echo 321 > sub/b
  $ hg add sub/b
  $ hg commit -m "second" sub/b

  $ cat sub/b
  321

  $ hg co 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ cat sub/b 2>/dev/null || echo "sub/b not present"
  sub/b not present

  $ test -d sub || echo "sub not present"
  sub not present