Improve validation of CI config entry if composite

lib/gitlab/ci/config/node/entry.rb

@@ -20,12 +20,8 @@ module Gitlab
           end
           def process!
-            return if leaf?
-            return unless valid?
-
-            compose!
-            process_nodes!
-            @validator.validate(:processed)
+            compose! unless leaf?
+            @validator.validate(:processed) if valid?
           end
           def leaf?
@@ -90,12 +86,12 @@ module Gitlab
           private
           def compose!
+            return unless valid?
+
             nodes.each do |key, essence|
               @nodes[key] = create_node(key, essence)
             end
-          end
-          def process_nodes!
             @nodes.each_value(&:process!)
           end

lib/gitlab/ci/config/node/jobs.rb

@@ -27,10 +27,6 @@ module Gitlab
             @nodes.values.any?(&:relevant?)
           end
-          def leaf?
-            false
-          end
-
           private
           def create_node(key, value)