Set (instead of compare) exresult

Interestingly this accidentally worked because `if exresult` is true for
both a non-empty string ("PASS") as well as a real `True` value.

Found by Mark Grassi as part of
https://gitlab.com/apparmor/apparmor/-/merge_requests/906

utils/test/test-parser-simple-tests.py

@@ -451,7 +451,7 @@ def parse_test_profiles(file_with_path):
         if line.startswith('#=EXRESULT '):
             exresult = line.split()[1]
             if exresult == 'PASS':
-                exresult == True
+                exresult = True
                 exresult_found = True
             elif exresult == 'FAIL':
                 exresult = False