allow user to specify provider for update task

[sirinek]

The tasks/update.json and tasks/update_windows.json files, as well as the powershell script to install updates define a parameter $provider that controls whether windows updates, chocolatey package updates or both get installed. However there is no way for the end user to select which, meaning the default of both get installed. In my specific case I only want windows updates, as we are using Puppet to control which versions of chocolatey packages should be installed on a host and cannot simply install the latest.