Prevent create volume from snapshot with bad size

Prevent to create a volume from a snapshot with a volume size less
than the snapshot size.

Check if a volume size is specified that it is less than
the snapshot size.

Raise a exception if it's lesser.

Fixes bug 1161841

Change-Id: Ic1afbfb025ce0b3906c35c6c50a71734d74a9851

cinder/volume/api.py

@@ -104,7 +104,10 @@ class API(base.Base):
                 raise exception.InvalidSnapshot(reason=msg)
             if not size:
                 size = snapshot['volume_size']
-
+            elif size < snapshot['volume_size']:
+                msg = _("Volume size cannot be lesser than"
+                        " the Snapshot size")
+                raise exception.InvalidInput(reason=msg)
             snapshot_id = snapshot['id']
         else:
             snapshot_id = None