watcher: fix checking of boot IDs

The recent change (commit 2151) to the watcher to make it handle offline
nodes also saves the offline attribute to the state file, but this is
not needed and also breaks the checking of the boot ID. This patch
simply removes it, restoring the correct behaviour.

Reviewed-by: imsnah

daemons/ganeti-watcher

@@ -340,7 +340,7 @@ class Watcher(object):
 
       # Keep changed boot IDs
       for name in check_nodes:
-        notepad.SetNodeBootID(name, self.bootids[name])
+        notepad.SetNodeBootID(name, self.bootids[name][0])
 
   def CheckInstances(self, notepad):
     """Make a pass over the list of instances, restarting downed ones.