Improve the error throws when a template to owned by a non root-admin is registered for all zones. (#11170)

Author: abh1sar

server/src/main/java/com/cloud/template/TemplateAdapterBase.java

@@ -192,7 +192,8 @@ public TemplateProfile prepare(boolean isIso, long userId, String name, String d
 
         if (!isAdmin && zoneIdList == null && !isRegionStore ) {
             // domain admin and user should also be able to register template on a region store
-            throw new InvalidParameterValueException("Please specify a valid zone Id. Only admins can create templates in all zones.");
+            throw new InvalidParameterValueException("Template registered for 'All zones' can only be owned a Root Admin account. " +
+                    "Please select specific zone(s).");
         }
 
         // check for the url format only when url is not null. url can be null incase of form based upload