APM-QA unit test bug fix

- temporary wav files created in temporary folder in TestExport.setUp()
- rename TestEchoPathSimulators -> TestExport

TBR=

Bug: webrtc:7494
Change-Id: I5b0c0675f539888e7392728055842c7772185921
Reviewed-on: https://webrtc-review.googlesource.com/14842
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20406}

modules/audio_processing/test/py_quality_assessment/quality_assessment/export_unittest.py

@@ -26,7 +26,7 @@ from . import simulation
 from . import test_data_generation_factory
 
 
-class TestEchoPathSimulators(unittest.TestCase):
+class TestExport(unittest.TestCase):
   """Unit tests for the export module.
   """
 
@@ -53,8 +53,8 @@ class TestEchoPathSimulators(unittest.TestCase):
     simulator.Run(
         config_filepaths=['apm_configs/default.json'],
         capture_input_filepaths=[
-            'pure_tone-440_1000.wav',
-            'pure_tone-880_1000.wav',
+            os.path.join(self._tmp_path, 'pure_tone-440_1000.wav'),
+            os.path.join(self._tmp_path, 'pure_tone-880_1000.wav'),
         ],
         test_data_generator_names=['identity', 'white_noise'],
         eval_score_names=['audio_level_peak', 'audio_level_mean'],