WARSAW, April 2 (Reuters) - Polish prosecutors have opened an investigation into a bomb attack that wounded a Polish soldier who was part of a U.N. peacekeeping patrol in Lebanon, the District Prosecutor's Office in Warsaw said on Thursday.The March 29 bombing was carried out in Bint Jubayl by an unidentified person using an improvised explosive device on the route of the Polish convoy, prosecutors said in a statement. The statement said the bomb attack failed due to the HMMWV, or Humvee, vehicl...