moving to global lazy loaded config

one of the problems we've got with tempest is the fact that config
loading is tied into the class hierarchy. However there is no
reason why it should be. If we instead create a config proxy
object we can lazy load the actual config when we are executing,
and not do it at import time.

This could use future iteration, but it does a huge job in
removing config from the object inheritance tree which massively
simplifies our ability to use config variables throughout the code.

Change-Id: I9b1bbfe231c85c01938bd68be4e5974bd24130d6
diff --git a/tempest/api/compute/volumes/test_attach_volume.py b/tempest/api/compute/volumes/test_attach_volume.py
index 660de95..c1ebc08 100644
--- a/tempest/api/compute/volumes/test_attach_volume.py
+++ b/tempest/api/compute/volumes/test_attach_volume.py
@@ -19,13 +19,15 @@
 
 from tempest.api.compute import base
 from tempest.common.utils.linux.remote_client import RemoteClient
-import tempest.config
+from tempest import config
 from tempest.test import attr
 
+CONF = config.CONF
+
 
 class AttachVolumeTestJSON(base.BaseV2ComputeTest):
     _interface = 'json'
-    run_ssh = tempest.config.TempestConfig().compute.run_ssh
+    run_ssh = CONF.compute.run_ssh
 
     def __init__(self, *args, **kwargs):
         super(AttachVolumeTestJSON, self).__init__(*args, **kwargs)