oeqa-runtime: add missing import os to ptest case

Add missing import os statement to the oeqa runtime ptest.py

(From OE-Core rev: e41c92c60694052c8292c1ea6b3d0b427aafafd7)

Signed-off-by: Stefan Kral <sk@typedivision.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/runtime/cases/ptest.py

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: MIT
 #
 
+import os
 import unittest
 import pprint
 import datetime