Fix diff output in test for Python 3

Signed-off-by: Saikrishna Arcot <[email protected]>

tests/hostcfgd/hostcfgd_passwh_test.py

@@ -123,7 +123,7 @@ def check_config(self, test_name, test_data, config_name):
         if not match:
             for name in files_to_compare:
                 diff_output += self.run_diff( sop_path + "/" + name,\
-                    op_path + "/" + name).decode('utf-8')
+                    op_path + "/" + name)
 
         self.assertTrue(len(diff_output) == 0, diff_output)