core.certmanager: Look for privkey.pem to go with fullchain.pem (fix #1526) This makes `prosodyctl cert import example.com /path/to/example.com/fullchain.pem` work. This was never intended to, yet users commonly tried this and got problems.

local xpcall = xpcall;

if select(2, xpcall(function (x) return x end, function () end,  "test")) ~= "test" then
	xpcall = require"util.compat".xpcall;
end

return {
	xpcall = xpcall;
};