remove useless anonymous field mentions

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)

engine/streams.go

@@ -23,8 +23,8 @@ func NewOutput() *Output {
 
 // Return true if something was written on this output
 func (o *Output) Used() bool {
-	o.Mutex.Lock()
-	defer o.Mutex.Unlock()
+	o.Lock()
+	defer o.Unlock()
 	return o.used
 }
 
@@ -32,8 +32,8 @@ func (o *Output) Used() bool {
 // to the output will be written to the new destination in addition to all the others.
 // This method is thread-safe.
 func (o *Output) Add(dst io.Writer) {
-	o.Mutex.Lock()
-	defer o.Mutex.Unlock()
+	o.Lock()
+	defer o.Unlock()
 	o.dests = append(o.dests, dst)
 }
 
@@ -42,8 +42,8 @@ func (o *Output) Add(dst io.Writer) {
 // destination in addition to all the others. This method is thread-safe.
 func (o *Output) Set(dst io.Writer) {
 	o.Close()
-	o.Mutex.Lock()
-	defer o.Mutex.Unlock()
+	o.Lock()
+	defer o.Unlock()
 	o.dests = []io.Writer{dst}
 }
 
@@ -96,8 +96,8 @@ func (o *Output) AddString(dst *string) error {
 // Write writes the same data to all registered destinations.
 // This method is thread-safe.
 func (o *Output) Write(p []byte) (n int, err error) {
-	o.Mutex.Lock()
-	defer o.Mutex.Unlock()
+	o.Lock()
+	defer o.Unlock()
 	o.used = true
 	var firstErr error
 	for _, dst := range o.dests {
@@ -113,8 +113,8 @@ func (o *Output) Write(p []byte) (n int, err error) {
 // AddTail and AddString tasks to complete.
 // The Close method of each destination is called if it exists.
 func (o *Output) Close() error {
-	o.Mutex.Lock()
-	defer o.Mutex.Unlock()
+	o.Lock()
+	defer o.Unlock()
 	var firstErr error
 	for _, dst := range o.dests {
 		if closer, ok := dst.(io.WriteCloser); ok {