When downgrading, templates are fully selected for install

[netniV]

Describe the bug

Recently, a change was made to default template installation as unticked unless the installation was brand new. This was to prevent issues with updating templates users may have modified and do not realise that they are reseting back to our defaults.

However, if you do downgrade, this change does not seem to take effect as it treats the template section like its a new install and fully selects all templates

To Reproduce

1. Use 1.2.x branch

2. Set cacti to 1.2.99 in the version table

3. Visit cacti and step through installation to template step

4. See all templates are selected

Expected behavior

As with upgrades, a downgrade should not select any templates