(Bloomberg) -- Junk-rated firms are rushing to reprice and refinance existing US-dollar debt, seizing on renewed investor appetite for riskier loans to slash borrowing costs. Most Read from BloombergInside a Year of Chaos and Conflict at Kevin Hart’s Media CompanyAmbani’s Cola War With Coke, Pepsi Spurs Fridge Bonanza in IndiaIran Makes New Offer on Uranium in Response to US, WSJ SaysNvidia’s CEO to Miss China Trip After Year of Travels With TrumpMore than 20 companies have kicked off deals to c