Fix test_file_readonly_change on macOS

[INFO]      [exec] FAIL nuxeo-drive-client/tests/test_readonly.py::TestReadOnly::test_file_readonly_change
[INFO]      [exec] =================================== FAILURES ===================================
[INFO]      [exec] ____________________ TestReadOnly.test_file_readonly_change ____________________
[INFO]      [exec] self = <tests.test_readonly.TestReadOnly testMethod=test_file_readonly_change>
[INFO]      [exec]     @skipIf(AbstractOSIntegration.is_windows(),
[INFO]      [exec]             'Readonly folder let new file creation')
[INFO]      [exec]     def test_file_readonly_change(self):
[INFO]      [exec]         local = self.local_client_1
[INFO]      [exec]         remote = self.remote_document_client_1
[INFO]      [exec]         # Create documents in the remote root workspace
[INFO]      [exec]         # then synchronize
[INFO]      [exec]         remote.make_folder('/', 'Test folder')
[INFO]      [exec]         remote.make_file('/Test folder', 'joe.odt', 'Some content')
[INFO]      [exec]         remote.make_file('/Test folder', 'jack.odt', 'Some content')
[INFO]      [exec]         remote.make_folder('/Test folder', 'Sub folder 1')
[INFO]      [exec]         remote.make_file('/Test folder/Sub folder 1', 'sub file 1.txt',
[INFO]      [exec]                          'Content')
[INFO]      [exec]         self._set_readonly_permission(self.user_1, TEST_WORKSPACE_PATH + '/Test folder', True)
[INFO]      [exec]         self.wait_sync(wait_for_async=True)
[INFO]      [exec]         self.assertTrue(local.exists('/Test folder'))
[INFO]      [exec]         self.assertTrue(local.exists('/Test folder/joe.odt'))
[INFO]      [exec]         self.assertTrue(local.exists('/Test folder/jack.odt'))
[INFO]      [exec]         self.assertTrue(local.exists('/Test folder/Sub folder 1'))
[INFO]      [exec]         self.assertTrue(local.exists('/Test folder/Sub folder 1/sub file 1.txt'))
[INFO]      [exec]         # Update the content on the server
[INFO]      [exec]         self.root_remote_client.update_content(TEST_WORKSPACE_PATH + '/Test folder/joe.odt',
[INFO]      [exec]                                                'Some remotely updated content', 'joe.odt')
[INFO]      [exec]         self.wait_sync(wait_for_async=True)
[INFO]      [exec]         self.assertTrue(local.get_content('/Test folder/joe.odt'), 'Some remotely updated content')
[INFO]      [exec]         # Remove the readonly
[INFO]      [exec]         self._set_readonly_permission(self.user_1, TEST_WORKSPACE_PATH + '/Test folder', False)
[INFO]      [exec]         self.wait_sync(wait_for_async=True)
[INFO]      [exec]         fname = os.path.join(self.sync_root_folder_1, 'Test folder', 'test.txt')
[INFO]      [exec]         fname2 = os.path.join(self.sync_root_folder_1, 'Test folder', 'Sub folder 1', 'test.txt')
[INFO]      [exec]         # Check it works
[INFO]      [exec]         self.assertTrue(self.touch(fname))
[INFO]      [exec]         self.assertTrue(self.touch(fname2))
[INFO]      [exec]         # First remove the files
[INFO]      [exec]         os.remove(fname)
[INFO]      [exec]         os.remove(fname2)
[INFO]      [exec]         # Put it back readonly
[INFO]      [exec]         self._set_readonly_permission(self.user_1, TEST_WORKSPACE_PATH + '/Test folder', True)
[INFO]      [exec]         self.wait_sync(wait_for_async=True)
[INFO]      [exec]         # Check it works
[INFO]      [exec]         self.assertFalse(self.touch(fname))
[INFO]      [exec] >       self.assertFalse(self.touch(fname2))
[INFO]      [exec] E       AssertionError: True is not false
[INFO]      [exec] fname      = '/Users/hudson/tmp/0ebd1d51/workspace/Drive_FT-drive_master-CUACR5UOIAO62W7K2CAAQ7UISS5UUL3SF5V2PSVOUZC4CRBQLRIA/tmp/tmpNb18hTdrive-1/Nuxeo Drive/Nuxeo Drive Test Workspace/Test folder/test.txt'
[INFO]      [exec] fname2     = '/Users/hudson/tmp/0ebd1d51/workspace/Drive_FT-drive_master-CUACR5UOIAO62W7K2CAAQ7UISS5UUL3SF5V2PSVOUZC4CRBQLRIA/tmp/tmpNb18hTdrive-1/Nuxeo Drive/Nuxeo Drive Test Workspace/Test folder/Sub folder 1/test.txt'
[INFO]      [exec] local      = <tests.mac_local_client.MacLocalClient object at 0x10d219ed0>
[INFO]      [exec] remote     = <RemoteDocumentClient base_folder=None, blob_timeout=60, check_suspended=None,...UL3SF5V2PSVOUZC4CRBQLRIA/tmp/tmpa4rLgi-nxdrive-uploads', user_id='driveuser_1'>
[INFO]      [exec] self       = <tests.test_readonly.TestReadOnly testMethod=test_file_readonly_change>
[INFO]      [exec] nuxeo-drive-client/tests/test_readonly.py:137: AssertionError