fix sonar problem

* Delete FIXME comment, because `string == ""` is beter than `len(string)` for checking string existence(by sonar)
* Remove duplicated code
* Fill empty block of code

core/config/json/json.go

@@ -210,7 +210,6 @@ func (c *JSONConfigContainer) String(key string) (string, error) {
 // DefaultString returns the string value for a given key.
 // if err != nil return defaultval
 func (c *JSONConfigContainer) DefaultString(key string, defaultVal string) string {
-	// TODO FIXME should not use "" to replace non existence
 	if v, err := c.String(key); v != "" && err == nil {
 		return v
 	}

core/logs/log.go

@@ -520,49 +520,19 @@ func (bl *BeeLogger) Debug(format string, v ...interface{}) {
 // Warn Log WARN level message.
 // compatibility alias for Warning()
 func (bl *BeeLogger) Warn(format string, v ...interface{}) {
-	if LevelWarn > bl.level {
-		return
-	}
-	lm := &LogMsg{
-		Level: LevelWarn,
-		Msg:   format,
-		When:  time.Now(),
-		Args:  v,
-	}
-
-	bl.writeMsg(lm)
+	bl.Warning(format, v...)
 }
 
 // Info Log INFO level message.
 // compatibility alias for Informational()
 func (bl *BeeLogger) Info(format string, v ...interface{}) {
-	if LevelInfo > bl.level {
-		return
-	}
-	lm := &LogMsg{
-		Level: LevelInfo,
-		Msg:   format,
-		When:  time.Now(),
-		Args:  v,
-	}
-
-	bl.writeMsg(lm)
+	bl.Informational(format, v...)
 }
 
 // Trace Log TRACE level message.
 // compatibility alias for Debug()
 func (bl *BeeLogger) Trace(format string, v ...interface{}) {
-	if LevelDebug > bl.level {
-		return
-	}
-	lm := &LogMsg{
-		Level: LevelDebug,
-		Msg:   format,
-		When:  time.Now(),
-		Args:  v,
-	}
-
-	bl.writeMsg(lm)
+	bl.Debug(format, v...)
 }
 
 // Flush flush all chan data.