app: Replace global zap logger

Signed-off-by: Evgenii Baidakov <evgenii@nspcc.io>

cmd/s3-gw/app_settings.go

@@ -413,6 +413,8 @@ func newLogger(v *viper.Viper) *Logger {
 		panic(fmt.Sprintf("build zap logger instance: %v", err))
 	}
 
+	zap.ReplaceGlobals(l)
+
 	return &Logger{
 		logger: l,
 		lvl:    c.Level,