Hector Mata/Agence France-Presse - Getty Images Senator John Kerry, who spent the weekend at his family's home in Nantucket, Mass., took his boat out for a Sunday morning ride. NANTUCKET, Mass., June 20 - Thwarted by fog, a flat bicycle tire and a tricky wind, Senator John Kerry spent most of a shortened Father's Day weekend secluded in his wife's seaside retreat here in one of the nation's most exclusive summer playgrounds. His Boeing 757 campaign plane was grounded in Washington on Friday night when the weather prevented landing at Nantucket's airstrip, which has seen only one jet of...