Add health probe endpoint flag/configuration (aws-controllers-k8s#137)

Part of aws-controllers-k8s/community#2012

This patch adds a new flag to all the controllers, allowing users and
operators to setup a healthz endpoint. Very rarely those flags (Healthz
and Metrics) and modified by users, so we're assigning them distinct ports
(8080 and 8081).

Signed-off-by: Amine Hilaly <hilalyamine@gmail.com>

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

pkg/config/config.go

@@ -42,6 +42,7 @@ const (
 	flagEnableLeaderElection           = "enable-leader-election"
 	flagLeaderElectionNamespace        = "leader-election-namespace"
 	flagMetricAddr                     = "metrics-addr"
+	flagHealthzAddr                    = "healthz-addr"
 	flagEnableDevLogging               = "enable-development-logging"
 	flagAWSRegion                      = "aws-region"
 	flagAWSEndpointURL                 = "aws-endpoint-url"
@@ -74,6 +75,7 @@ var (
 // Config contains configuration options for ACK service controllers
 type Config struct {
 	MetricsAddr                    string
+	HealthzAddr                    string
 	EnableLeaderElection           bool
 	LeaderElectionNamespace        string
 	EnableDevelopmentLogging       bool
@@ -99,6 +101,11 @@ func (cfg *Config) BindFlags() {
 		"0.0.0.0:8080",
 		"The address the metric endpoint binds to.",
 	)
+	flag.StringVar(
+		&cfg.HealthzAddr, flagHealthzAddr,
+		"0.0.0.0:8081",
+		"The address the health probe endpoint binds to.",
+	)
 	flag.BoolVar(
 		&cfg.EnableWebhookServer, flagEnableWebhookServer,
 		false,