FOREX-Safe-haven yen and Swiss franc gain on Ukraine worries

* Escalation of Ukraine tensions pushes up yen, Swiss franc * Euro hits 21-month low against Swiss franc * German inflation eyed LONDON, Aug 28 (Reuters) - The yen and Swiss franc gained on Thursday, while the euro fell, as concerns about a serious escalation in tensions between Ukraine and Russia rattled investors and drove them to seek safe-haven currencies.