Login don't pause terminal when using callback

[jcubic]

Expected behavior

I should not see password: again when login in

Actual behavior

The terminal is not paused when I log in, so I see the password: prompt again.

Steps to reproduce

function delay(n) {
    return new Promise(resolve => setTimeout(resolve, n));
}
$(function() {
    $('body').terminal($.noop, {
        greetings: 'Welcome ' + id,
        name: 'term_' + id,
        login: function(u, p, c) {
            delay(5000).then(() => c(u + ':' + p));
        }
    });
});

found when trying to reproduce the issue from #537