Return the changed path as an argument to the watch callback. This is useful

for the test CD, and simplifies DevController everso slightly.  It ought to be
generally useful, too.
 
Signed-off-by: Ewan Mellor <ewan@xensource.com>

tools/python/xen/xend/XendDomain.py

@@ -114,7 +114,7 @@ class XendDomain:
 
     ## private:
 
-    def onReleaseDomain(self):
+    def onReleaseDomain(self, _):
         self.domains_lock.acquire()
         try:
             self.refresh()

tools/python/xen/xend/XendDomainInfo.py

@@ -424,7 +424,7 @@ class XendDomainInfo:
             return []
 
 
-    def storeChanged(self):
+    def storeChanged(self, _):
         log.trace("XendDomainInfo.storeChanged");
 
         changed = False

tools/python/xen/xend/server/DevController.py

@@ -328,7 +328,7 @@ class DevController:
             ev = Event()
             result = { 'status': Timeout }
             
-            xswatch(statusPath, hotplugStatusCallback, statusPath, ev, result)
+            xswatch(statusPath, hotplugStatusCallback, ev, result)
 
             ev.wait(DEVICE_CREATE_TIMEOUT)
             return result['status']

tools/python/xen/xend/xenstore/xswatch.py

@@ -51,7 +51,7 @@ def watchMain():
         try:
             we = xs.read_watch()
             watch = we[1]
-            res = watch.fn(*watch.args, **watch.kwargs)
+            res = watch.fn(we[0], *watch.args, **watch.kwargs)
             if not res:
                 watch.unwatch()
         except: