ClientUserTransaction should log cause exceptions

When org.jboss.tm.usertx.client.ClientUserTransaction encounters exceptions,
it should at least log them at debug level, otherwise important cause exceptions
and stacktraces are lost. So, code like this:

catch (RemoteException e)

{ // destroy session gone bad. destroySession(); throw new SystemException(e.toString()); }

catch (Exception e)

{ throw new SystemException(e.toString()); }

Should become:

catch (RemoteException e)

{ // destroy session gone bad. destroySession(); log.debug("Remote exception encountered while....", e); throw new SystemException(e.toString()); }

catch (Exception e)

{ log.debug("Exception encountered while...", e); throw new SystemException(e.toString()); }