HARARE, June 16 (Reuters) – Zimbabwe’s President Emmerson Mnangagwa has ordered the central bank to stop foreign currency borrowing, as the government battles to contain a plunge in the local currency ahead of a general election. Mnangagwa faces a tough bid for re-election in an Aug. 23 vote amid surging inflation and a Zimdollar that has weakened by more than 80% since the beginning of the year.