Fix the return value of blkdev_name_to_number().
  - Function blkdev_name_to_number() should return both devname and devnum, 
otherwise it may cause "unpack non-sequence" error.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>

diff -r 0972fc23b504 tools/python/xen/util/blkif.py
--- a/tools/python/xen/util/blkif.py	Sat Jun 28 16:29:00 2008 +0100
+++ b/tools/python/xen/util/blkif.py	Mon Jun 30 17:06:51 2008 +0800
@@ -20,7 +20,7 @@ def blkdev_name_to_number(name):
     devnum = None
 
     try:
-        return os.stat(n).st_rdev
+        return (devname, os.stat(n).st_rdev)
     except Exception, ex:
         pass