Ex-Qwest Exec Tom Hall to Plead Guilty  DENVER (Reuters) - Former Qwest Communications Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=Q.N target=/stocks/quickinfo/fullquote"&gt;Q.N&lt;/A&gt;  executive Tom Hall, who was scheduled to go on trial next month  on charges stemming from an accounting scandal, will plead  guilty, his attorney said on Friday.