Fix perf issue using WSMan provider or Get-PSSessionConfiguration

[SteveL-MSFT]

PR Summary

.NET Core introduced a perf regression during instantiation of ServiceController which is used by the WSMan Config Provider to check if WinRM is running as it depends on WinRM to get configuration information.

Instead of creating new instance of ServiceController every time we need to check WinRM service status. We can create it just once and use the Refresh() method on the instance to get latest status information. This brings the perf back to comparable to Windows PowerShell.

Prior to this change, Windows PowerShell calling Get-PSSessionConfiguration took ~3 secs and PSCore6.1 took ~14 secs. After this change, PSCore6.1 took ~4 secs.

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[PaulHigin]

LGTM