fsmonitor: avoid needless instantiation of dirstate

Using repo.local() instead of util.safehasattr(repo, 'dirstate') also
avoids executing setup procedures for remote repository (including
statichttprepo).

This is reason why this patch also removes a part of subsequent
comment, and try/except for AttributeError at accessing to repo.wvfs.

hgext/fsmonitor/__init__.py

@@ -677,17 +677,13 b' def reposetup(ui, repo):'
                       'extension and has been disabled.\n') % ext)
             return
 
-    if util.safehasattr(repo, 'dirstate'):
-        # We don't work with subrepos either. Note that we can get passed in
-        # e.g. a statichttprepo, which throws on trying to access the substate.
-        # XXX This sucks.
-        try:
+    if repo.local():
+        # We don't work with subrepos either.
+        #
             # if repo[None].substate can cause a dirstate parse, which is too
             # slow. Instead, look for a file called hgsubstate,
             if repo.wvfs.exists('.hgsubstate') or repo.wvfs.exists('.hgsub'):
                 return
-        except AttributeError:
-            return
 
         fsmonitorstate = state.state(repo)
         if fsmonitorstate.mode == 'off':