pkg/archive: fix TempArchive cleanup w/ one read

This fixes the removal of TempArchives which can read with only one
read. Such archives weren't getting removed because EOF wasn't being
triggered.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)

pkg/archive/archive.go

@@ -742,17 +742,20 @@ func NewTempArchive(src Archive, dir string) (*TempArchive, error) {
 		return nil, err
 	}
 	size := st.Size()
-	return &TempArchive{f, size}, nil
+	return &TempArchive{f, size, 0}, nil
 }
 
 type TempArchive struct {
 	*os.File
 	Size int64 // Pre-computed from Stat().Size() as a convenience
+	read int64
 }
 
 func (archive *TempArchive) Read(data []byte) (int, error) {
 	n, err := archive.File.Read(data)
-	if err != nil {
+	archive.read += int64(n)
+	if err != nil || archive.read == archive.Size {
+		archive.File.Close()
 		os.Remove(archive.File.Name())
 	}
 	return n, err