Support server groups with launch-node.py

If a cloud is setup to use server groups, then select it based on the
group we pass via the CLI.

Change-Id: I2662af9daa39024a306d6e60eb8c71a450b67701
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

launch/launch-node.py

@@ -113,6 +113,9 @@ def build_server(cloud, name, group, image, flavor,
                  volume_size, timeout):
     key = None
     server = None
+    _group = None
+    if group:
+        _group = cloud.get_server_group(group)
 
     create_kwargs = dict(image=image, flavor=flavor, name=name,
                          reuse_ips=False, wait=True,
@@ -120,7 +123,7 @@ def build_server(cloud, name, group, image, flavor,
                          volume_size=volume_size,
                          network=network,
                          config_drive=config_drive,
-                         timeout=timeout)
+                         timeout=timeout, group=_group)
 
     if availability_zone:
         create_kwargs['availability_zone'] = availability_zone