Delta Fails to Get OK from Bond Holders  NEW YORK (Reuters) - Delta Air Lines Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=DAL.N target=/stocks/quickinfo/fullquote"&gt;DAL.N&lt;/A&gt; on Friday  said it hit another bump in its effort to avoid bankruptcy as  bond holders refused to give it permission to buy back certain  debt it needs restructured, sending its shares down about 3  percent.