Product Form: Show clear error message for duplicated GTIN/UPC/EAN/ISBN#16146

itsmeichigo merged 2 commits intotrunkwoocommerce/woocommerce-ios:trunkfrom

woomob-1349-ios-app-shows-generic-network-error-instead-of-user-friendlywoocommerce/woocommerce-ios:woomob-1349-ios-app-shows-generic-network-error-instead-of-user-friendlyCopy head branch name to clipboard