Scenario: Skip TestServerMultinode when only 1 compute node

This scenario is useless if we only have one compute node. It should
be skipped.

Change-Id: I5a287d708f6de958c24ca811e741c7dd68197c22
diff --git a/tempest/scenario/test_server_multinode.py b/tempest/scenario/test_server_multinode.py
index 7e0e41c..f21ff4f 100644
--- a/tempest/scenario/test_server_multinode.py
+++ b/tempest/scenario/test_server_multinode.py
@@ -31,6 +31,14 @@
     credentials = ['primary', 'admin']
 
     @classmethod
+    def skip_checks(cls):
+        super(TestServerMultinode, cls).skip_checks()
+
+        if CONF.compute.min_compute_nodes < 2:
+            raise cls.skipException(
+                "Less than 2 compute nodes, skipping multinode tests.")
+
+    @classmethod
     def setup_clients(cls):
         super(TestServerMultinode, cls).setup_clients()
         # Use admin client by default