BCD uninstaller is run more than once

[Agostino Russo]

BCD uninstaller is run once per each drive and subsequent invocations fail

04-03 15:17 DEBUG TaskList: ## Running Remove bootloader entry...
04-03 15:17 DEBUG WindowsBackend: undo_bootini C:
04-03 15:17 DEBUG WindowsBackend: undo_configsys Drive(C: hd 113277.621094 mb free )
04-03 15:17 DEBUG WindowsBackend: Removing bcd entry {3455fe3e-a4f9-11dd-87a4-001c2568a34f}
04-03 15:17 DEBUG WindowsBackend: undo_bootini F:
04-03 15:17 DEBUG WindowsBackend: undo_configsys Drive(F: removable 0.0 mb free )
04-03 15:17 DEBUG WindowsBackend: Removing bcd entry {3455fe3e-a4f9-11dd-87a4-001c2568a34f}
04-03 15:17 ERROR TaskList: Error executing command
>>command=C:\Windows\System32\bcdedit.exe /delete {3455fe3e-a4f9-11dd-87a4-001c2568a34f} /f
>>retval=1
>>stderr=An error occurred while attempting to delete the specified entry.

The system cannot find the file specified.

>>stdout=
Traceback (most recent call last):
  File "Z:\home\evan\bzr\wubi.trunk\build\wubi\files\lib\wubi\backends\common\tasklist.py", line 196, in __call__
  File "Z:\home\evan\bzr\wubi.trunk\build\wubi\files\lib\wubi\backends\win32\backend.py", line 491, in undo_bootloader
  File "Z:\home\evan\bzr\wubi.trunk\build\wubi\files\lib\wubi\backends\win32\backend.py", line 668, in undo_bcd
  File "Z:\home\evan\bzr\wubi.trunk\build\wubi\files\lib\wubi\backends\common\utils.py", line 60, in run_command
Exception: Error executing command
>>command=C:\Windows\System32\bcdedit.exe /delete {3455fe3e-a4f9-11dd-87a4-001c2568a34f} /f

[Agostino Russo (ago)]

Fix committed in r110 but, although I did not experience any regression, I do not have vista handy at the moment, so further testing is required.