run-tests: remove useless "failed" flag from addOutputMismatch()

It never be set to True.

tests/run-tests.py

@@ -1350,7 +1350,6 b' class TestResult(unittest._TextTestResul'
             return
 
         accepted = False
-        failed = False
         lines = []
 
         with iolock:
@@ -1391,7 +1390,7 b' class TestResult(unittest._TextTestResul'
                     else:
                         rename(test.errpath, '%s.out' % test.path)
                     accepted = True
-            if not accepted and not failed:
+            if not accepted:
                 self.faildata[test.name] = b''.join(lines)
 
         return accepted