Provide the option to not to log via STDERR

Today, Multus will always log via STDERR, and these logs will then
logged by the Kubelet. If we also choose to have Multus log to a file by
setting the LogFile option in the CNI configuration, the same logs will
be logged twice.

This commit provide the option to disable logging to STDERR.

Signed-off-by: Yun Zhou <yunz@nvidia.com>

pkg/types/conf.go

@@ -257,7 +257,8 @@ func GetGatewayFromResult(result *current.Result) []net.IP {
 
 // LoadNetConf converts inputs (i.e. stdin) to NetConf
 func LoadNetConf(bytes []byte) (*NetConf, error) {
-	netconf := &NetConf{}
+	// LogToStderr's default value set to true
+	netconf := &NetConf{LogToStderr: true}
 
 	logging.Debugf("LoadNetConf: %s", string(bytes))
 	if err := json.Unmarshal(bytes, netconf); err != nil {
@@ -265,6 +266,7 @@ func LoadNetConf(bytes []byte) (*NetConf, error) {
 	}
 
 	// Logging
+	logging.SetLogStderr(netconf.LogToStderr)
 	if netconf.LogFile != "" {
 		logging.SetLogFile(netconf.LogFile)
 	}

pkg/types/types.go

@@ -43,6 +43,7 @@ type NetConf struct {
 	DefaultNetworks []string                 `json:"defaultNetworks"`
 	LogFile         string                   `json:"logFile"`
 	LogLevel        string                   `json:"logLevel"`
+	LogToStderr     bool                     `json:"logToStderr,omitempty"`
 	RuntimeConfig   *RuntimeConfig           `json:"runtimeConfig,omitempty"`
 	// Default network readiness options
 	ReadinessIndicatorFile string `json:"readinessindicatorfile"`