Convert compute api tests to global CONF object

This commit takes all the uses of config in the compute api tests and
converts them to use the global CONF object.

Partially implements bp config-cleanup

Change-Id: Iac92d6ac88200222392a131b4c95411594c509ba
diff --git a/tempest/api/compute/test_extensions.py b/tempest/api/compute/test_extensions.py
index aac635c..55146e5 100644
--- a/tempest/api/compute/test_extensions.py
+++ b/tempest/api/compute/test_extensions.py
@@ -15,9 +15,12 @@
 
 
 from tempest.api.compute import base
+from tempest import config
 from tempest.openstack.common import log as logging
 from tempest import test
 
+CONF = config.CONF
+
 
 LOG = logging.getLogger(__name__)
 
@@ -28,11 +31,11 @@
     @test.attr(type='gate')
     def test_list_extensions(self):
         # List of all extensions
-        if len(self.config.compute_feature_enabled.api_extensions) == 0:
+        if len(CONF.compute_feature_enabled.api_extensions) == 0:
             raise self.skipException('There are not any extensions configured')
         resp, extensions = self.extensions_client.list_extensions()
         self.assertEqual(200, resp.status)
-        ext = self.config.compute_feature_enabled.api_extensions[0]
+        ext = CONF.compute_feature_enabled.api_extensions[0]
         if ext == 'all':
             self.assertIn('Hosts', map(lambda x: x['name'], extensions))
         elif ext: