warning when not running "xm" as root

hello,

Currently -unstable requires user must be root to run xm. But the error spit out is not clear enough, or even misleaded ("Error: Error connecting to xend, is xend running?")

This patch checks to see if the user is root, and warns if not (patched against cset 1.1440)

===== tools/python/xen/xm/main.py 1.52 vs edited =====

@@ -129,6 +129,8 @@
         sys.exit(1)
 
     def main(self, args):
+        if os.geteuid() != 0:
+            self.err("xm must be run as root.")
         try:
             self.main_call(args)
         except socket.error, ex: