* Aim is for central bank to once again influence interest rates* Zimbabwe ditched its own currency in 2009 due to hyperinflation* Money market rates chaotic since thenBy MacDonald DzirutweHARARE, March 22 (Reuters) - The African Export-Import Bank (Afrexim) on Saturday gave Zimbabwe a $100 million loan to allow its central bank to set up an inter-bank market for the first time in five years, whic