Fix test_collection.py when it fails early

[INFO]      [exec] _____ ERROR at teardown of TestCollection.test_collection_synchronization _____
[INFO]      [exec] self = <tests.test_collection.TestCollection testMethod=test_collection_synchronization>
[INFO]      [exec]     def tearDown(self):
[INFO]      [exec] >       self.remote_document_client_1.delete(self.collection["uid"], use_trash=False)
[INFO]      [exec] E       AttributeError: 'TestCollection' object has no attribute 'collection'
[INFO]      [exec] __class__  = <class 'tests.test_collection.TestCollection'>
[INFO]      [exec] self       = <tests.test_collection.TestCollection testMethod=test_collection_synchronization>
[INFO]      [exec] tests\test_collection.py:7: AttributeError