Split resource_setup for compute tests

Split up the resource_setup method for all the compute tests, as per the
latest spec.

Partially-implements bp:resource-cleanup

Change-Id: I6562534ca5eb5e33c6f8d6cbcac5e7735535916a
diff --git a/tempest/api/compute/images/test_images.py b/tempest/api/compute/images/test_images.py
index 396d629..c29c40d 100644
--- a/tempest/api/compute/images/test_images.py
+++ b/tempest/api/compute/images/test_images.py
@@ -23,17 +23,19 @@
 class ImagesTestJSON(base.BaseV2ComputeTest):
 
     @classmethod
-    def resource_setup(cls):
-        super(ImagesTestJSON, cls).resource_setup()
+    def skip_checks(cls):
+        super(ImagesTestJSON, cls).skip_checks()
         if not CONF.service_available.glance:
             skip_msg = ("%s skipped as glance is not available" % cls.__name__)
             raise cls.skipException(skip_msg)
-
         if not CONF.compute_feature_enabled.snapshot:
             skip_msg = ("%s skipped as instance snapshotting is not supported"
                         % cls.__name__)
             raise cls.skipException(skip_msg)
 
+    @classmethod
+    def setup_clients(cls):
+        super(ImagesTestJSON, cls).setup_clients()
         cls.client = cls.images_client
         cls.servers_client = cls.servers_client