Remove skips in test server rescue

* Remove skips test_rescued_vm_add_remove_security_group
* Fixes two issues
    1. In remove_security_group pass self.sg_name instead of sg_id which was
        failing earlier.
    2. Before executing unrescue server operation, the server status seems to
       be active hence the bug 1126257. So adding a rescue operation at the
       start of the test to fix the bug

Fixes bug 1126257

Change-Id: Ie79b94b9cde0f35bb4ea5955bc284139d85123cb
diff --git a/tempest/tests/compute/servers/test_server_rescue.py b/tempest/tests/compute/servers/test_server_rescue.py
index 91010ce..97766e0 100644
--- a/tempest/tests/compute/servers/test_server_rescue.py
+++ b/tempest/tests/compute/servers/test_server_rescue.py
@@ -15,8 +15,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import testtools
-
 from tempest.common.utils.data_utils import rand_name
 import tempest.config
 from tempest import exceptions
@@ -193,8 +191,12 @@
         self.assertEqual(202, resp.status)
 
     @attr(type='positive')
-    @testtools.skip("Skipped until Bug #1126257 is resolved")
     def test_rescued_vm_add_remove_security_group(self):
+        # Rescue the server
+        self.servers_client.rescue_server(
+            self.server_id, self.password)
+        self.servers_client.wait_for_server_status(self.server_id, 'RESCUE')
+
         #Add Security group
         resp, body = self.servers_client.add_security_group(self.server_id,
                                                             self.sg_name)
@@ -202,7 +204,7 @@
 
         #Delete Security group
         resp, body = self.servers_client.remove_security_group(self.server_id,
-                                                               self.sg_id)
+                                                               self.sg_name)
         self.assertEqual(202, resp.status)
 
         # Unrescue the server