use winrm-elevated by default to run chef-client as a scheduled task

[hh]

Chef-dk introduced a bug in 0.18.26 (most likely due to upgrading the versions of the winrm gems) that results in the fallowing:

    - write file C:\chef\install.ps1 on base-2012r2-2016-08-01
    [base-2012r2-2016-08-01] File C:\chef\install.ps1 cannot be loaded because running scripts is disabled on this system. For more information, see about_Execution_Policies at http://go.microsoft.com/fwlink/?LinkID=135170.
                             At line:1 char:3
                             + & "C:\chef\install.ps1"
                             +   ~~~~~~~~~~~~~~~~~~~~~
                                 + CategoryInfo          : SecurityError: (:) [], PSSecurityException
                                 + FullyQualifiedErrorId : UnauthorizedAccess

See https://github.com/WinRb/winrm-elevated and probably somewhere around https://github.com/chef/chef-provisioning-aws/blob/master/lib/chef/provisioning/aws_driver/driver.rb#L1101

[hh]

https://discourse.chef.io/t/how-to-use-knife-winrm-with-elevated-privileges/9467/2 has some info