Execute the protractor engine

@method
@static
@param {string[]} args
@param {Function} callback
function (args, callback) {
            let child = this
                .runProtractor(args)
                .on('exit', function (code) {
                    if (child) {
                        child.kill();
                    }

                    if (callback) {
                        callback(code);
                    }
                });
        }