Checks that master instance has the most recent
version of all the BIG-IP instances

@param {Object} instances - Instances map
function markVersions(instances) {
        let highestVersion = '0.0.0';
        let instance;

        Object.keys(instances).forEach((instanceId) => {
            instance = instances[instanceId];
            if (instance.version && util.versionCompare(instance.version, highestVersion) > 0) {
                highestVersion = instance.version;
            }
        });

        Object.keys(instances).forEach((instanceId) => {
            instance = instances[instanceId];
            if (!instance.version || util.versionCompare(instance.version, highestVersion) === 0) {
                instance.versionOk = true;
            } else {
                instance.versionOk = false;
            }
        });
    }