Only attempt loading the ES template if ES output is enabled

It used to raise an error if any template setting was set but
the ES output wasn't enabled. This caused problems with the new
Metricbeat config, which sets template settings in the configuration.

Also removes the code that enables the template loading on `-setup`,
because template loading is by default enabled anyway.

Fixes elastic#4435.

libbeat/beat/beat.go

@@ -459,17 +459,6 @@ func (b *Beat) loadDashboards() error {
 // the elasticsearch output. It is important the the registration happens before
 // the publisher is created.
 func (b *Beat) registerTemplateLoading() error {
-	if *setup {
-		// -setup implies template.enabled=true
-		if b.Config.Template == nil {
-			b.Config.Template = common.NewConfig()
-		}
-		err := b.Config.Template.SetBool("enabled", -1, true)
-		if err != nil {
-			return fmt.Errorf("Error setting template.enabled=true: %v", err)
-		}
-	}
-
 	// Check if outputting to file is enabled, and output to file if it is
 	if b.Config.Template != nil && b.Config.Template.Enabled() {
 		var cfg template.TemplateConfig
@@ -495,33 +484,31 @@ func (b *Beat) registerTemplateLoading() error {
 
 	esConfig := b.Config.Output["elasticsearch"]
 	// Loads template by default if esOutput is enabled
-	if (b.Config.Template == nil && esConfig.Enabled()) || (b.Config.Template != nil && b.Config.Template.Enabled()) {
-		if esConfig == nil || !esConfig.Enabled() {
-			return fmt.Errorf("Template loading requested but the Elasticsearch output is not configured/enabled")
-		}
-
-		// load template through callback to make sure it is also loaded
-		// on reconnecting
-		callback := func(esClient *elasticsearch.Client) error {
-
-			if b.Config.Template == nil {
-				b.Config.Template = common.NewConfig()
+	if esConfig != nil && esConfig.Enabled() {
+		if b.Config.Template == nil || (b.Config.Template != nil && b.Config.Template.Enabled()) {
+			// load template through callback to make sure it is also loaded
+			// on reconnecting
+			callback := func(esClient *elasticsearch.Client) error {
+
+				if b.Config.Template == nil {
+					b.Config.Template = common.NewConfig()
+				}
+
+				loader, err := template.NewLoader(b.Config.Template, esClient, b.Info)
+				if err != nil {
+					return fmt.Errorf("Error creating Elasticsearch template loader: %v", err)
+				}
+
+				err = loader.Load()
+				if err != nil {
+					return fmt.Errorf("Error loading Elasticsearch template: %v", err)
+				}
+
+				return nil
 			}
 
-			loader, err := template.NewLoader(b.Config.Template, esClient, b.Info)
-			if err != nil {
-				return fmt.Errorf("Error creating Elasticsearch template loader: %v", err)
-			}
-
-			err = loader.Load()
-			if err != nil {
-				return fmt.Errorf("Error loading Elasticsearch template: %v", err)
-			}
-
-			return nil
+			elasticsearch.RegisterConnectCallback(callback)
 		}
-
-		elasticsearch.RegisterConnectCallback(callback)
 	}
 
 	return nil