LONDON (Reuters) -Three days of strikes by tens of thousands of British rail workers over the next week have been suspended while “intensive negotiations” are held in a long-running dispute over pay and working conditions, the RMT trade union said on Friday. Rail operators welcomed the news but said the change of plan had come too late in the day to reinstate services on Saturday, and transport minister Mark Harper warned there would still be “significant disruption”. The RMT, whose members have held several days of walkouts over the last few months, said it would hold talks with the train ope…