Update only the given Job property. Intendeed to prevent conflicts with two sources updating the same job at the same time, but different properties: - uuid - the job's uuid - prop - the name of the property to update - val - value to assign to such property - meta - Any additional information to pass to the backend which is not job properties - callback - f(err) called with error if something fails, otherwise with null.
function updateJobProperty(
            uuid,
            prop,
            val,
            meta,
            callback)
        {

            if (typeof (meta) === 'function') {
                callback = meta;
                meta = {};
            }

            if (!jobs[uuid]) {
                return callback(new e.BackendResourceNotFoundError(sprintf(
                  'Job with uuid \'%s\' does not exist', uuid)));
            } else {
                jobs[uuid][prop] = val;
                return callback(null);
            }
        }