[#540] Add md5 S3Tests compatability

Signed-off-by: Pavel Pogodaev <p.pogodaev@yadro.com>

api/handler/put.go

@@ -251,7 +251,7 @@ func (h *handler) PutObjectHandler(w http.ResponseWriter, r *http.Request) {
 		Reader:            body,
 		Header:            metadata,
 		Encryption:        encryptionParams,
-		ContentMD5:        r.Header.Get(api.ContentMD5),
+		ContentMD5:        getMD5Header(r),
 		ContentSHA256Hash: r.Header.Get(api.AmzContentSha256),
 	}
 
@@ -1038,3 +1038,13 @@ func (h *handler) parseLocationConstraint(r *http.Request) (*createBucketParams,
 	}
 	return params, nil
 }
+
+func getMD5Header(r *http.Request) *string {
+	var md5Hdr *string
+	if len(r.Header.Values(api.ContentMD5)) != 0 {
+		hdr := r.Header.Get(api.ContentMD5)
+		md5Hdr = &hdr
+	}
+
+	return md5Hdr
+}