tests: Drop os.system calls

Use python native code instead. This seems to avoid an occasional
crash or abort of some sort with latest libosinfo

tests/clitest.py

@@ -1420,8 +1420,8 @@ def cleanup():
     Cleanup temporary files used for testing
     """
     for i in clean_files:
-        os.system("chmod 777 %s > /dev/null 2>&1" % i)
-        os.system("rm -rf %s > /dev/null 2>&1" % i)
+        if os.path.exists(i):
+            os.unlink(i)
 
 
 class CLITests(unittest.TestCase):

tests/clonetest.py

@@ -35,7 +35,7 @@ class TestClone(unittest.TestCase):
 
     def setUp(self):
         for f in local_files:
-            os.system("touch %s" % f)
+            open(f, "w").write("")
 
     def tearDown(self):
         for f in local_files: