Add GetObjectNInfo to object layer (#6449)

The new call combines GetObjectInfo and GetObject, and returns an
object with a ReadCloser interface.

Also adds a number of end-to-end encryption tests at the handler
level.

cmd/xl-sets.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"hash/crc32"
 	"io"
+	"net/http"
 	"sort"
 	"strings"
 	"sync"
@@ -578,6 +579,11 @@ func (s *xlSets) ListBuckets(ctx context.Context) (buckets []BucketInfo, err err
 
 // --- Object Operations ---
 
+// GetObjectNInfo - returns object info and locked object ReadCloser
+func (s *xlSets) GetObjectNInfo(ctx context.Context, bucket, object string, rs *HTTPRangeSpec, h http.Header) (gr *GetObjectReader, err error) {
+	return s.getHashedSet(object).GetObjectNInfo(ctx, bucket, object, rs, h)
+}
+
 // GetObject - reads an object from the hashedSet based on the object name.
 func (s *xlSets) GetObject(ctx context.Context, bucket, object string, startOffset int64, length int64, writer io.Writer, etag string, opts ObjectOptions) error {
 	return s.getHashedSet(object).GetObject(ctx, bucket, object, startOffset, length, writer, etag, opts)