logger: fix wrong callback method

Fix wrong callback in `logger.go`, and add test cases:

1. `logger.Warningln` should call `logger.Warnln`, not `logger.Warn`.

2. It's ok for `logger.Print` to call `entry.Info`, but calling `entry.Print`
   is better.

Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>

logger.go

@@ -200,7 +200,7 @@ func (logger *Logger) Info(args ...interface{}) {
 
 func (logger *Logger) Print(args ...interface{}) {
 	entry := logger.newEntry()
-	entry.Info(args...)
+	entry.Print(args...)
 	logger.releaseEntry(entry)
 }
 
@@ -256,7 +256,7 @@ func (logger *Logger) Warnln(args ...interface{}) {
 }
 
 func (logger *Logger) Warningln(args ...interface{}) {
-	logger.Warn(args...)
+	logger.Warnln(args...)
 }
 
 func (logger *Logger) Errorln(args ...interface{}) {