Enable the Glance Artifact repository by default

Since Murano now requires Glance Artifact Repository to be its package
storage the appropriate UI setting is set by default.

The 'murano_glance_artifacts_plugin' additional component setting is
modified to not be restricted to experimental deployments and its
default value is set to True.

Change-Id: Ieaa373d52403b834aa17eeb05a70b37c61454ad0
Closes-Bug: #1556133

nailgun/nailgun/fixtures/openstack.yaml

@@ -946,7 +946,7 @@
               - condition: "not ('experimental' in version:feature_groups)"
                 action: "hide"
           murano_glance_artifacts_plugin:
-            value: false
+            value: true
             label: "Enable glance artifact repository"
             description: "If selected glance artifact repository will be enabled"
             weight: 40
@@ -954,8 +954,6 @@
             restrictions:
               - condition: "settings:additional_components.murano.value == false"
                 message: "Murano should be enabled"
-              - condition: "not ('experimental' in version:feature_groups)"
-                action: "hide"
           heat:
             value: true
             label: ""