Magento 2 Cron Job Error – Not Configured Yet

I am running Magento 2.1.0 on Lamp-Ubuntu 16.04 with PHP 7.0.8.

I am getting an error while installing a new theme using system > web setup wizard > component manager.

In the readiness check process I am getting the following errors:

Cron script readiness check failed. 

Error from Setup Application Cron Script:
Cron job has not been configured yet
Other checks will fail as a result (PHP version, PHP settings, and PHP extensions)

Error from Updater Application Cron Script:
Cron job has not been configured yet

I had created a cron job, not sure I have done it correctly (I am newbie in Linux platform). Here is how I created the cron job:

In terminal:

crontab -u user -e

and then I added the following contents:

*/5 * * * * /usr/bin/php /var/www/html/ecommerce/bin/magento cron:run | grep -v "Ran jobs by schedule" >> /var/www/html/ecommerce/var/log/magento.cron.log
*/5 * * * * /usr/bin/php /var/www/html/ecommerce/update/cron.php >> /var/www/html/ecommerce/var/log/update.cron.log
*/5 * * * * /usr/bin/php /var/www/html/ecommerce/bin/magento setup:cron:run >> /var/www/html/ecommerce/var/log/setup.cron.log

I got this from official Magento documentation, I changed the php and magento directory according to my setup.

But I am still getting this error. How can I check whether those jobs are running?

Is there anything else I should do? Should I create any files ?

I added the following job below those 3 jobs for testing purpose

*/5 * * * * /usr/bin/php /var/www/html/ecommerce/testcron/testcron.php >> /var/www/html/ecommerce/testcron/cron.out

testcron.php:

<?php
    echo "Hello " ;
?>

cron.out file was working fine (showing the text hello).

So whats the problem with those 3 jobs?