Fixes the multi-backend skip bug and the cleanup steps

The multi-backend test class and the tests within should now be
skipped correctly also when running on python 2.6. Also fixes
a cleanup problem occurring in case of error in setUpClass and
speed things up by not creating the 2nd volume/type if backends
have the same name (in which case only part of the tests can be
executed).

Change-Id: Ibeb961ea000bb1d1034f857a64552c7aa75ed4d5
Fixes: bug #1177608
diff --git a/tempest/config.py b/tempest/config.py
index 7164b95..f7620bd 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -318,12 +318,12 @@
                help="Catalog type of the Volume Service"),
     cfg.BoolOpt('multi_backend_enabled',
                 default=False,
-                help="Runs Cinder multi-backend test (requires 2 backend)"),
+                help="Runs Cinder multi-backend test (requires 2 backends)"),
     cfg.StrOpt('backend1_name',
-               default='LVM_iSCSI',
+               default='BACKEND_1',
                help="Name of the backend1 (must be declared in cinder.conf)"),
     cfg.StrOpt('backend2_name',
-               default='LVM_iSCSI_1',
+               default='BACKEND_2',
                help="Name of the backend2 (must be declared in cinder.conf)"),
 ]