Add tests for TimeZone cmdlets and FileCatalog cmdlets [SD:717473]

test/powershell/Modules/Microsoft.PowerShell.Management/Clear-EventLog.Tests.ps1

@@ -1,4 +1,4 @@
-if ($IsWindows) {
+if ($IsWindows -and !$IsCore) {
   #check to see whether we're running as admin in Windows...
   $windowsIdentity = [Security.Principal.WindowsIdentity]::GetCurrent()
   $windowsPrincipal = new-object 'Security.Principal.WindowsPrincipal' $windowsIdentity
@@ -28,4 +28,4 @@ if ($IsWindows) {
       } catch {$_.FullyQualifiedErrorId      | Should Be "Microsoft.PowerShell.Commands.ClearEventLogCommand"}
     }
   }
-}
+}