A bidding war among the world’s leading cosmetics groups for hair care group Wella AG looked imminent on Tuesday after one suitor, Germany’s Henkel, bought a stake in the company.Henkel’s purchase of a nearly 7% stake in its smaller rival came after reports that the Stroeher family, which controls nearly 80% of Wella, was finally prepared to sell and that Procter & Gamble had made an approach.“This move by Henkel is an attempt to force the family to run an auction fo...