Fix null-valued expression error

[NAshwini]

Signed-off-by: NAshwini ashwini.nehate@msystechnologies.com

Description

Fix null-valued expression error for powershell command. This code change will now work for both Chef Client and Chef Infra Client i.e till 14.x and 15.x

Stacktrace

Execution Error:
Where-Object : You cannot call a method on a null-valued expression.
At C:\Packages\Plugins\Chef.Bootstrap.WindowsAzure.ChefClient\1210.13.2.1\bin\chef-install.psm1:30 char:40
+ ... lass Win32_Product | Where-Object { $_.Name.contains("Chef Client") }
+                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Where-Object], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull,Microsoft.PowerShell.Commands.WhereObjectCommand