check_test_cases: Avoid removing duplicated test cases

One of the jobs of check_test_cases is to check for duplicate test
descriptions and to have them ordered:

 * Stop using a set to collect the different test cases from the
   test scripts.

Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
diff --git a/tests/scripts/check_test_cases.py b/tests/scripts/check_test_cases.py
index 2dddf7a..4a3ecef 100755
--- a/tests/scripts/check_test_cases.py
+++ b/tests/scripts/check_test_cases.py
@@ -105,11 +105,14 @@
         listed = subprocess.check_output(['sh', file_name, '--list-test-cases'])
         # Assume test file is responsible for printing identical format of
         # test case description between --list-test-cases and its OUTCOME.CSV
-        listed = set(map(lambda x: x.rstrip(), listed.splitlines()))
+        #
         # idx indicates the number of test case since there is no line number
         # in `compat.sh` for each test case.
-        for idx, description in enumerate(listed):
-            self.process_test_case(descriptions, file_name, idx, description)
+        for idx, description in enumerate(listed.splitlines()):
+            self.process_test_case(descriptions,
+                                   file_name,
+                                   idx,
+                                   description.rstrip())
 
     @staticmethod
     def collect_test_directories():