Fix import group ordering in test_utils.py

Per the hacking guidelines the ordering for imports should be stdlib
first, followed by 3rd party imports, and last should the project
imports. However, test_utils.py did not adhere to this ordering. This
commit fixes the oversight.

Change-Id: I0fcc9d137706e841c2e22bd2af8ecd77135c78d2
Merge "Fix import group ordering in test_utils.py"