Mark etcd-quorum-read as deprecated.

staging/src/k8s.io/apiserver/pkg/server/options/etcd.go

@@ -144,7 +144,8 @@ func (s *EtcdOptions) AddFlags(fs *pflag.FlagSet) {
 		"SSL Certificate Authority file used to secure etcd communication.")
 
 	fs.BoolVar(&s.StorageConfig.Quorum, "etcd-quorum-read", s.StorageConfig.Quorum,
-		"If true, enable quorum read.")
+		"If true, enable quorum read. It defaults to true and is strongly recommended not setting to false.")
+	fs.MarkDeprecated("etcd-quorum-read", "This flag is deprecated and the ability to switch off quorum read will be removed in a future release.")
 
 	fs.StringVar(&s.EncryptionProviderConfigFilepath, "experimental-encryption-provider-config", s.EncryptionProviderConfigFilepath,
 		"The file containing configuration for encryption providers to be used for storing secrets in etcd")