Check if JEADSC-resources are available

[TuemmlerKelch]

In some cases, JEADSC module isn't properly loaded, which results in the necessary resources not being available.
The following command should return two results:

(Get-DscResource -Module jeadsc).name

JeaRoleCapabilities
JeaSessionConfiguration

If that's not the case; JEA-configurator will fail and revert.