Remove all usage of six library

Replace six with Python 3 style code.

Change-Id: I724eba28d1a88317655f9cb7da94716772cd01ab
diff --git a/manila_tempest_tests/common/waiters.py b/manila_tempest_tests/common/waiters.py
index 5d8d344..056dab6 100644
--- a/manila_tempest_tests/common/waiters.py
+++ b/manila_tempest_tests/common/waiters.py
@@ -15,7 +15,6 @@
 
 import time
 
-import six
 from tempest import config
 from tempest.lib import exceptions
 
@@ -137,7 +136,7 @@
                            'dest': dest_host,
                            'share_id': share['id'],
                            'timeout': client.build_timeout,
-                           'status': six.text_type(statuses),
+                           'status': str(statuses),
                        })
             raise exceptions.TimeoutException(message)
     return share