Run Glance initialization when Glance is enabled, not just registry

Per [1] Glance registry should not be required to run since Queens.

[1] https://specs.openstack.org/openstack/glance-specs/specs/queens/approved/glance/deprecate-registry.html

Change-Id: I5477c8769ff4ae151d4d6ccb5e5d8dd5788909b0
Closes-bug: #1859847
diff --git a/stack.sh b/stack.sh
index 089510f..dee84fa 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1155,7 +1155,7 @@
 # Glance
 # ------
 
-if is_service_enabled g-reg; then
+if is_glance_enabled; then
     echo_summary "Configuring Glance"
     init_glance
 fi
@@ -1280,7 +1280,7 @@
 # scripts as userdata.
 # See https://help.ubuntu.com/community/CloudInit for more on ``cloud-init``
 
-if is_service_enabled g-reg; then
+if is_glance_enabled; then
 
     echo_summary "Uploading images"