morestatus: don't crash with different drive letters for repo.root and CWD

Previously, if there were unresolved files and the CWD drive was different from
the repo drive, `hg status -v` would page the normal status, followed by the
exception header.  A stacktrace was waiting when the pager exited.  The
underlying cause was the same as f445b10dc7fb.

Unfortunately, I don't see any reasonable way to write a test this [1].

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-November/107401.html

mercurial/cmdutil.py

@@ -570,9 +570,8 b' def _conflictsmsg(repo):'
     unresolvedlist = [f for f in mergestate.unresolved() if m(f)]
     if unresolvedlist:
         mergeliststr = '\n'.join(
-            ['    %s' % os.path.relpath(
-                os.path.join(repo.root, path),
-                pycompat.getcwd()) for path in unresolvedlist])
+            ['    %s' % util.pathto(repo.root, pycompat.getcwd(), path)
+             for path in unresolvedlist])
         msg = _('''Unresolved merge conflicts:
 
 %s