Call options.Freeze in replication_util.

- Missed this in crrev.com/c/1898378

TEST=run_tests scripts/replication_util_unittest
BUG=chromium:1021252

Change-Id: Iae05e108072d0f7ef18b36fb04dbcaac492be523
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1921097
Tested-by: Andrew Lamb <andrewlamb@chromium.org>
Auto-Submit: Andrew Lamb <andrewlamb@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/replication_util.py b/scripts/replication_util.py
index f9d7083..a7a3ccc 100644
--- a/scripts/replication_util.py
+++ b/scripts/replication_util.py
@@ -41,5 +41,6 @@
 def main(argv):
   parser = GetParser()
   options = parser.parse_args(argv)
+  options.Freeze()
 
   options.func(options)