runc init: fix double call to ConfigureLogs

I have noticed that ConfigureLogs do not return an error in case logging
was already configured -- instead it just warns about it. So I went
ahead and changed the warning to the actual error...

... only to discover I broke things badly, because in case of runc init
logging is configured twice. The fix is to not configure logging in case
we are init.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/logs/logs.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"sync"
 
+	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
 
@@ -64,8 +65,7 @@ func ConfigureLogging(config Config) error {
 	defer configureMutex.Unlock()
 
 	if loggingConfigured {
-		logrus.Debug("logging has already been configured")
-		return nil
+		return errors.New("logging has already been configured")
 	}
 
 	logrus.SetLevel(config.LogLevel)

main.go

@@ -150,6 +150,10 @@ func main() {
 		if err := reviseRootDir(context); err != nil {
 			return err
 		}
+		// let init configure logging on its own
+		if args := context.Args(); args != nil && args.First() == "init" {
+			return nil
+		}
 		return logs.ConfigureLogging(createLogConfig(context))
 	}