By Tommy Wilkes and John O’Donnell LONDON/FRANKFURT (Reuters) – Russian President Vladimir Putin’s vow to cut customers off from its gas unless they start paying in roubles is more of a ‘bluff’ to ward off further sanctions than a genuine threat to stop supplying energy, according to European officials and analysts. Gas was flowing to Europe normally on Friday, and some experts reckon the new arrangement may be broadly the same as the old process of paying, with only a slight boost for the embattled Russian currency. Below is an outline of why, for now at least, Putin’s gas ultimatum is consid…