WaitForCertificateServices: Add read-only parameter 'Available'

[johlju]

Details of the scenario you tried and the problem that is occurring:
Suggest we add a read-only parameter to the WaitForCertificateServices resource. That way the Get-TargetResource could call Test-TargetResource and return the result (the actual current state) of the certificate services in the property Available when calling Get-DscConfiguration.

The DSC configuration that is using the resource (as detailed as possible):

        WaitForCertificateServices RootCA
        {
            CARootName   = 'test-dc01-ca'
            CAServerFQDN = 'dc01.test.pha'
        }

Version of the Operating System and PowerShell the DSC Target Node is running:
n/a

Version of the DSC module you're using, or 'dev' if you're using current dev branch:
Dev