Federal agents issued a half-dozen subpoenas yesterday to associates of the Rev. Al Sharpton ordering them to appear this month before a New York grand jury. The feds are also looking for documents relating to Sharpton’s failed bid for president in 2004 and some related business entities. Sharpton seemed surprised by it all, but his lawyer, Michael Hardy, provided the best quote of the day yesterday when he told the AP that no one was especially concerned. “I can’t think of a time when the Rev. Sharpton wasn’t under investigation,” he said.