Issue 2423: Fix ClassCastException in OracleChangeNotificationListener.remove() method (eclipse-ee4j#2427)

- use unwrap to get the underlying OracleConnection

(cherry picked from commit e62e78a)
Signed-off-by: Patrick Schmitt <[email protected]>

Author: Zuplyx

foundation/org.eclipse.persistence.oracle/src/main/java/org/eclipse/persistence/platform/database/oracle/dcn/OracleChangeNotificationListener.java

@@ -248,13 +248,15 @@ public void remove(Session session) {
         Accessor accessor = databaseSession.getAccessor();
         accessor.incrementCallCount(databaseSession);
         try {
-            OracleConnection connection = (OracleConnection)databaseSession.getServerPlatform().unwrapConnection(accessor.getConnection());
+            OracleConnection connection = databaseSession.getServerPlatform().unwrapConnection(accessor.getConnection()).unwrap(OracleConnection.class);
             databaseSession.log(SessionLog.FINEST, SessionLog.CONNECTION, "dcn_unregister");
             try {
                 connection.unregisterDatabaseChangeNotification(this.register);
             } catch (SQLException exception) {
                 throw DatabaseException.sqlException(exception, databaseSession.getAccessor(), databaseSession, false);
             }
+        } catch (SQLException e) {
+            throw DatabaseException.sqlException(e, databaseSession.getAccessor(), databaseSession, false);
         } finally {
             accessor.decrementCallCount();
         }