Williams Ends Bid to Sell Power Business  NEW YORK (Reuters) - Williams Cos. Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WMB.N target=/stocks/quickinfo/fullquote"&gt;WMB.N&lt;/A&gt; has  scrapped efforts to sell its power business as the depressed  wholesale market has damaged prospects for selling the unit,  the natural gas company said on Thursday.