Pull Request for Issues #21574 (part "No user after installation" and "Workflow missing tables" #21582 .

Summary of Changes

• Change default NOW() of columns modified and created to 0000-00-00 00:00:00 (like common in Joomla)

Testing Instructions

I don't know exactly if it's a MySql version issue or not.

• Provider All-Inkl.

• PHP version 7.1.19-nmm1 and 7.2.7

• MySql 5.5.58-nmm1-log

• Install nightly build FULL package of 2018-08-12 or 2018-08-13 where com_workflow is already merged.

• During installation don't check option to delete /installation/ folder.

• After installation check database tables #__users, #__workflow, #__workflow_stages, #__workflow_transitions.

• They are empty or missing but shouldn't.

• You cannot login in backend.

• Delete file configuration.php.

• Change file installation/sql/mysql/joomla.sql like done in this PR.

• Start a new installation by reloading the Joomla page.

• Check again.

• All fine.

Expected result

• Complete installation.
• Empty or no /administrator/logs/error.php after installation.
• No Congratulations message after install(!!) Not part of this pr!

Actual result

"Invalid default value for 'created'"

error.php shows the following stack trace after installation

CRITICAL ... error	Uncaught Throwable of type 

Joomla\Database\Exception\PrepareStatementFailureException thrown with message "Invalid default value for 'created'".

Stack trace:

#0 .../libraries/vendor/joomla/database/src/Mysqli/MysqliDriver.php(873): Joomla\Database\Mysqli\MysqliStatement->__construct(Object(mysqli), 'CREATE TABLE IF...')

#1 .../libraries/vendor/joomla/database/src/DatabaseDriver.php(1778): Joomla\Database\Mysqli\MysqliDriver->prepareStatement('CREATE TABLE IF...')

#2 .../installation/src/Model/DatabaseModel.php(1126): Joomla\Database\DatabaseDriver->setQuery(Object(Joomla\Database\Mysqli\MysqliQuery))

#3 .../installation/src/Model/DatabaseModel.php(565): Joomla\CMS\Installation\Model\DatabaseModel->populateDatabase(Object(Joomla\Database\Mysqli\MysqliDriver), 'sql/mysql/jooml...')

#4 .../installation/src/Model/ConfigurationModel.php(71): Joomla\CMS\Installation\Model\DatabaseModel->createTables(Object(stdClass))

#5 .../installation/src/Controller/InstallationController.php(95): Joomla\CMS\Installation\Model\ConfigurationModel->setup(Object(stdClass))

#6 .../libraries/src/MVC/Controller/BaseController.php(717): Joomla\CMS\Installation\Controller\InstallationController->config()

#7 .../installation/src/Application/InstallationApplication.php(316): Joomla\CMS\MVC\Controller\BaseController->execute('config')

#8 .../installation/src/Application/InstallationApplication.php(202): Joomla\CMS\Installation\Application\InstallationApplication->executeController()

#9 .../installation/src/Application/InstallationApplication.php(231): Joomla\CMS\Installation\Application\InstallationApplication->dispatch()

#10 .../installation/src/Application/InstallationApplication.php(246): Joomla\CMS\Installation\Application\InstallationApplication->doExecute()

#11 .../installation/includes/app.php(65): Joomla\CMS\Installation\Application\InstallationApplication->execute()

#12 .../installation/index.php(36): require_once('/www/htdocs/w00...')

#13 {main}

This means DatabaseModel::populateDatabase() dies silently

Additional comment

• No Congratulations message after install(!!) Not part of this pr!