Berlin (AFP) – From swastikas sprayed on the walls to Hitler salute selfies, far-right provocations are a growing problem at the sites of former Nazi concentration camps in Germany.Museum directors have sounded the alarm over a spike in incidents, which include visitors writing messages of Holocaust denial in the guestbook and challenging tour guides on the facts of the genocide.”Messages glorifying Nazism or demanding the camps be reopened for foreigners have become more common,” Volkhard Knigge, museum director at the former Buchenwald concentration camp in eastern Germany, told AFP.”There h…