By Sedara Oluwadara Sebastien Haller has left Borussia Dortmund's pre-season training camp in Switzerland after a tumour was found in his testicle, says the German club.   The 28-year-old Ivory Coast international recently joined the Bundesliga side from Dutch club Ajax.     Dortmund said Haller "complained that he felt unwell after training on Monday" and, following medical tests, "a testicular tumour" was discovered.   Further examinations will now take place "over the coming days".   "This news today came as a shock to Sebastien Haller and everyone else," said Dortmund sporting director Sebastian Kehl.   "The entire BVB