Reload the cron container instead of restarting it

According to the current execution flow of `cron-command`, whenever any new cron job is added, it restarts the `easyengine/cron` container to accommodate the new changes. This can disrupt the cycle of already running cron-jobs.

For example, if a job is running every 10 minutes and had completed say 9 minutes before restart was executed, then it's time will start from zero again. Thus, the executing cron cycles could get a little affected by this.

A reloading signal or a HUP signal to refresh and accommodate the new changes is required to replace the current restart method.