Doesn't remove the variables on uninstall.

Implemented patch for the issue

/*
* Implementation hook_uninstall().
*/
function job_scheduler_uninstall() {
db_query("DELETE FROM {variable} WHERE name LIKE 'job_scheduler%'");
}

job scheduler generates variables dynamically. if you might have observed it with feeds module to adding importer id so variable_del('job_scheduler_rebuild_all'); is not sufficient.

JobScheduler.inc:      $class = variable_get('job_scheduler_class_'. $name, 'JobScheduler');
job_scheduler.module:  if (variable_get('job_scheduler_rebuild_all', FALSE)) {
 job_scheduler.module:  if (variable_get('job_scheduler_rebuild_all', FALSE)) {
contrib/job_scheduler]$grep variable_set -r *
job_scheduler.module:    variable_set('job_scheduler_rebuild_all', FALSE);
job_scheduler.module:  variable_set('job_scheduler_rebuild_all', TRUE);

I have considered and tested to use 
db_query("DELETE FROM {variable} WHERE name LIKE 'job_scheduler%'");