[#441] Don't produce extra object.Head request at regular object upload

Hash can be calculated locally in S3 gateway.
Creation epoch used for versioning and will be
fetched during get and list requests. To avoid
conflicts, put method do not update cache anymore.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

api/layer/object_test.go

@@ -1,8 +1,10 @@
 package layer
 
 import (
+	"bytes"
 	"crypto/rand"
 	"crypto/sha256"
+	"io/ioutil"
 	"testing"
 
 	"github.com/nspcc-dev/neofs-s3-gw/api/data"
@@ -112,3 +114,21 @@ func TestTrimAfterObjectID(t *testing.T) {
 		require.Nil(t, actual)
 	})
 }
+
+func TestWrapReader(t *testing.T) {
+	src := make([]byte, 1024*1024+1)
+	_, err := rand.Read(src)
+	require.NoError(t, err)
+	h := sha256.Sum256(src)
+
+	streamHash := sha256.New()
+	reader := bytes.NewReader(src)
+	wrappedReader := wrapReader(reader, 64*1024, func(buf []byte) {
+		streamHash.Write(buf)
+	})
+
+	dst, err := ioutil.ReadAll(wrappedReader)
+	require.NoError(t, err)
+	require.Equal(t, src, dst)
+	require.Equal(t, h[:], streamHash.Sum(nil))
+}