[receiver/zookeeper] Use component.UseLocalHostAsDefaultHost feature gate (open-telemetry#30868)

**Description:** Fixes open-telemetry#30867

Author: mx-psi

.chloggen/mx-psi_internal-localhostgate.yaml

@@ -25,6 +25,7 @@ subtext: |
     - receiver/splunk_hec
     - receiver/awsxray
     - receiver/influxdb
+    - receiver/zookeeper
 
 # If your change doesn't affect end users or the exported elements of any package,
 # you should instead start your pull request title with [chore] or use the "Skip Changelog" label.

receiver/zookeeperreceiver/README.md

@@ -19,7 +19,7 @@ to be enabled for the receiver to be able to collect metrics.
 
 ## Configuration
 
-- `endpoint`: (default = `:2181`) Endpoint to connect to collect metrics. Takes the form `host:port`.
+- `endpoint`: (default = `0.0.0.0:2181`) Endpoint to connect to collect metrics. Takes the form `host:port`. The `component.UseLocalHostAsDefaultHost` feature gate changes this to localhost:2181. This will become the default in a future release.
 - `timeout`: (default = `10s`) Timeout within which requests should be completed.
 - `initial_delay` (default = `1s`): defines how long this receiver waits before starting.
 

receiver/zookeeperreceiver/factory.go

@@ -13,10 +13,12 @@ import (
 	"go.opentelemetry.io/collector/receiver"
 	"go.opentelemetry.io/collector/receiver/scraperhelper"
 
+	"github.com/open-telemetry/opentelemetry-collector-contrib/internal/common/localhostgate"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/zookeeperreceiver/internal/metadata"
 )
 
 const (
+	defaultPort               = 2181
 	defaultCollectionInterval = 10 * time.Second
 	defaultTimeout            = 10 * time.Second
 )
@@ -37,7 +39,7 @@ func createDefaultConfig() component.Config {
 	return &Config{
 		ScraperControllerSettings: cfg,
 		TCPAddr: confignet.TCPAddr{
-			Endpoint: ":2181",
+			Endpoint: localhostgate.EndpointForPort(defaultPort),
 		},
 		MetricsBuilderConfig: metadata.DefaultMetricsBuilderConfig(),
 	}

receiver/zookeeperreceiver/factory_test.go

@@ -26,7 +26,7 @@ func TestFactory(t *testing.T) {
 	// Assert defaults.
 	assert.Equal(t, 10*time.Second, rCfg.CollectionInterval)
 	assert.Equal(t, 10*time.Second, rCfg.Timeout)
-	assert.Equal(t, ":2181", rCfg.Endpoint)
+	assert.Equal(t, "0.0.0.0:2181", rCfg.Endpoint)
 
 	tests := []struct {
 		name    string