Add negative test for get server in test_servers_negative.py.

This adds test for getting invalid server instance details
Fixes bug 1130519

Change-Id: I5df981700c549b0db04c06d823547f6fbb15f610
diff --git a/tempest/tests/compute/servers/test_servers_negative.py b/tempest/tests/compute/servers/test_servers_negative.py
index 9b528f6..553af78 100644
--- a/tempest/tests/compute/servers/test_servers_negative.py
+++ b/tempest/tests/compute/servers/test_servers_negative.py
@@ -287,3 +287,9 @@
             pass
         else:
             self.fail('Server was created with nonexistent security group')
+
+    @attr(type='negative')
+    def test_get_non_existent_server(self):
+        # Get a non existent server details
+        self.assertRaises(exceptions.NotFound, self.client.get_server,
+                          '999erra43')