qubes/storage: support on-line resize

Call `qubes.ResizeDisk` qrexec service after resizing volume, to adjust
filesystem size there.

qubes/storage/__init__.py

@@ -309,6 +309,9 @@ class Storage(object):
         if isinstance(volume, basestring):
             volume = self.vm.volumes[volume]
         self.get_pool(volume).resize(volume, size)
+        if self.vm.is_running():
+            self.vm.run_service('qubes.ResizeDisk', input=volume.name,
+                user='root', wait=True)
 
     def create(self):
         ''' Creates volumes on disk '''