Interim Premier Mehdi Jomâa received, on Thursday, a phone call from German Foreign Minister Frank-Walter Steinmeier who congratulated him on taking office.   The German FM praised the move which he said is "likely to help finish off the transition process in Tunisia."     The German government "trusts the ability of the Tunisian people to smooth out difficulties and convey a bright image of its revolution," Frank-Walter Steinmeier said. The German Foreign Minister expressed his country's willingness to keep up a high pace of cooperation with Tunisia and back up the current cabinet for the sake of the country and its democratic transition, a Presidency press release indicated.