Only respond to watches that originated from xswatch.
diff -r ec03b24a2d83 tools/python/xen/xend/xenstore/xswatch.py
--- a/tools/python/xen/xend/xenstore/xswatch.py	Tue Aug 15 19:53:55 2006 +0100
+++ b/tools/python/xen/xend/xenstore/xswatch.py	Mon Aug 28 11:04:43 2006 -0700
@@ -63,9 +63,10 @@ def watchMain():
         try:
             we = xs.read_watch()
             watch = we[1]
-            res = watch.fn(we[0], *watch.args, **watch.kwargs)
-            if not res:
-                watch.unwatch()
+            if watch.__class__ == xswatch: 
+                res = watch.fn(we[0], *watch.args, **watch.kwargs)
+                if not res:
+                    watch.unwatch()
         except:
             log.exception("read_watch failed")
             # Ignore this exception -- there's no point throwing it