Added support for horizon_launch_instance_defaults

This variable allows customizing the default values for properties found
in the Launch Instance modal, using the LAUNCH_INSTANCE_DEFAULTS config
option.

Change-Id: I1a795b788b3fbc78e814c93f56fd996090c7463b

defaults/main.yml

@@ -180,6 +180,14 @@ horizon_default_role_name: _member_
 ## Launch instance
 horizon_launch_instance_legacy: False
 horizon_launch_instance_ng: True
+horizon_launch_instance_defaults:
+  config_drive: False
+  enable_scheduler_hints: True
+  disable_image: False
+  disable_instance_snapshot: False
+  disable_volume: False
+  disable_volume_snapshot: False
+  create_volume: True
 
 ## Ironic UI Panel
 horizon_enable_ironic_ui: False

releasenotes/notes/launch-instance-defaults-support-533844543082b2f4.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - It is now possible to use the horizon_launch_instance_defaults variable
+    that allows customizing the default values for properties found in the
+    Launch Instance modal, using the LAUNCH_INSTANCE_DEFAULTS config option.
+    See https://docs.openstack.org/developer/horizon/install/settings.html#launch-instance-defaults

templates/horizon_local_settings.py.j2

@@ -247,6 +247,10 @@ OPENSTACK_ENABLE_PASSWORD_RETRIEVE = {{ horizon_enable_password_retrieve }}
 LAUNCH_INSTANCE_LEGACY_ENABLED = {{ horizon_launch_instance_legacy }}
 LAUNCH_INSTANCE_NG_ENABLED = {{ horizon_launch_instance_ng }}
 
+# A dictionary of settings which can be used to provide the default values for
+# properties found in the Launch Instance modal.
+LAUNCH_INSTANCE_DEFAULTS = {{ horizon_launch_instance_defaults }}
+
 # The Xen Hypervisor has the ability to set the mount point for volumes
 # attached to instances (other Hypervisors currently do not). Setting
 # can_set_mount_point to True will add the option to set the mount point