OID attributes get a wrong name when normalized due to first dot not being removed (#446)

Co-authored-by: Alejandro Maura Bonet <alejandro.maura-bonet@t-systems.com>

Author: baconjander

src/main/java/org/apache/xml/security/utils/RFC2253Parser.java

@@ -166,8 +166,8 @@ static String normalizeAT(String str) {
 
         String at = str.toUpperCase().trim();
 
-        if (at.startsWith("OID")) {
-            at = at.substring(3);
+        if (at.startsWith("OID.")) {
+            at = at.substring(4);
         }
 
         return at;