ActiveDirectoryDsc: Split meta tests and init tests in different AppVeyor jobs

[johlju]

There are issue running unit tests when stubs are not able to be loaded, see the
#245 (comment). One solution that can mitigate this would be to split the jobs.

See example over at SqlServerDsc https://github.com/PowerShell/SqlServerDsc/blob/dev/appveyor.yml

[johlju]

A test was removed from the new resource ADDomainFunctionalLevel since the build worker could not run it due to worng classes was loaded on the buildworker. It works when using the stub classes, but not a build worker that running Windows Server 2012 R2 and loads a class with missing enum types.

This issue should resolve this and then this test should be able to be re-added.

                    Context 'When desired domain mode should be ''Windows2016Domain''' {
                        BeforeAll {
                            Mock -CommandName Set-ADDomainMode
                            Mock -CommandName Compare-TargetResourceState -MockWith {
                                return @(
                                    @{
                                        ParameterName  = 'DomainMode'
                                        Actual  = 'Windows2012R2Domain'
                                        Expected  = 'Windows2016Domain'
                                        InDesiredState = $false
                                    }
                                )
                            }

                            $setTargetResourceParameters = $mockDefaultParameters.Clone()
                            $setTargetResourceParameters['DomainMode'] = 'Windows2016Domain'
                        }

                        It 'Should not throw and call the correct mocks' {
                            { Set-TargetResource @setTargetResourceParameters } | Should -Not -Throw

                            Assert-MockCalled -CommandName Compare-TargetResourceState -Exactly -Times 1 -Scope It
                            Assert-MockCalled -CommandName Set-ADDomainMode -Exactly -Times 1 -Scope It
                        }
                    }

Error on the build worker

        Context When desired domain mode should be 'Windows2016Domain'
VERBOSE: The domain functional level will change from 'Windows2012R2Domain' to 'Windows2016Domain'. (ADDCP0005)
          [-] Should not throw and call the correct mocks 69ms
            Expected no exception to be thrown, but an exception "Cannot process argument transformation on parameter 'DomainMode'. Cannot convert null to type "Microsoft.ActiveDirectory.Management.ADDomainMode" due to enumeration values that are not valid. Specify one of the following enumeration values and try again. The possible enumeration values are "Windows2000Domain,Windows2003InterimDomain,Windows2003Domain,Windows2008Domain,Windows2008R2Domain,Windows2012Domain,Windows2012R2Domain,UnknownDomain"." was thrown from C:\projects\activedirectorydsc\Tests\Unit\MSFT_ADDomainFunctionalLevel.Tests.ps1:261 char:31
                + ...             { Set-TargetResource @setTargetResourceParameters } | Sho ...
                +                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.
            261:                             { Set-TargetResource @setTargetResourceParameters } | Should -Not -Throw
            at <ScriptBlock>, C:\projects\activedirectorydsc\Tests\Unit\MSFT_ADDomainFunctionalLevel.Tests.ps1: line 261
Executing script C:\projects\activedirectorydsc\Tests\Unit\MSFT_ADDomainTrust.Tests.ps1