Update Test-IsNanoServer to use reliable method about psdscresources

[TravisEz13]

Required function to make above code work

function Test-Command 
{
    param 
    (
        [String] $Name 
    )

    return ($null -ne (Get-Command -Name $Name -ErrorAction Continue 2> $null))
} 

Note: This doesn't use silently continue because it was designed to work with version of PowerShell before it existed