Fix up chef_gem immediate execution

- Uses Chef::Resource.after_created hook to trigger Chef::Resource.run_action
    This inadvertently prevents any notifications by skipping Chef::Runner.run_action
- Falls back to find_gem_by_path only if we are on omnibus and using gem_package (not chef_gem)

chef/lib/chef/provider/package/rubygems.rb

@@ -312,7 +312,7 @@ def initialize(new_resource, run_context=nil)
             end
             @gem_env = AlternateGemEnvironment.new(new_resource.gem_binary)
             Chef::Log.debug("#{@new_resource} using gem '#{new_resource.gem_binary}'")
-          elsif is_omnibus?
+          elsif is_omnibus? && (!@new_resource.instance_of? Chef::Resource::ChefGem)
             # Opscode Omnibus - The ruby that ships inside omnibus is only used for Chef
             # Default to installing somewhere more functional
             gem_location = find_gem_by_path

chef/lib/chef/resource/chef_gem.rb

@@ -40,29 +40,13 @@ def gem_binary(arg=nil)
         nil
       end
 
-      def action(arg=nil)
-        if arg
-          action_list = arg.kind_of?(Array) ? arg : [ arg ]
-          action_list = action_list.collect { |a| a.to_sym }
-          action_list.each do |action|
-            validate(
-              {
-                :action => action,
-              },
-              {
-                :action => { :kind_of => Symbol, :equal_to => @allowed_actions },
-              }
-            )
-          end
-
-          # chef_gem actions should run immediately so that the result affects the recipe evaluation
-          action_list.each do |action|
-            self.run_action(action)
-          end
-          @action = action_list
-        else
-          @action
+      def after_created
+        # Chef::Resource.run_action: Caveat: this skips Chef::Runner.run_action, where notifications are handled
+        # Action could be an array of symbols, but probably won't (think install + enable for a package)
+        Array(@action).each do |action|
+          self.run_action(action)
         end
+        Gem.clear_paths
       end
     end
   end