Final tiny fix of unused import

Threw out unused import of shutil.

qubesmanager/backup.py

@@ -23,7 +23,6 @@
 import traceback
 
 import signal
-import shutil
 
 from qubesadmin import Qubes, exc
 from qubesadmin import utils as admin_utils

qubesmanager/restore.py

@@ -21,7 +21,6 @@
 #
 
 import sys
-import shutil
 from PyQt4 import QtCore  # pylint: disable=import-error
 from PyQt4 import QtGui  # pylint: disable=import-error
 import threading