lint: fix wrong-import-order warnings

Newer pylint is able to enforce PEP8 module ordering.  Respect it.

BUG=chromium:863669
TEST=`cros lint` no longer reports this

Change-Id: I4d4f7669d6dcced7e0d1ceeffd949a818b867055
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1768870
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/autotest_quickmerge_unittest.py b/scripts/autotest_quickmerge_unittest.py
index 9c09c96..8b8d4c3 100644
--- a/scripts/autotest_quickmerge_unittest.py
+++ b/scripts/autotest_quickmerge_unittest.py
@@ -7,9 +7,10 @@
 
 from __future__ import print_function
 
-import mock
 import types
 
+import mock
+
 from chromite.lib import cros_test_lib
 from chromite.scripts import autotest_quickmerge