PR Summary

In a multi-threaded environment there is a NullReferenceException in DSC ClearCache().
This fix is needed for GuestConfig.

PR Context

Initial values for fields marked with ThreadStaticAttribute should not be used, because such initialization occurs only once, when the class constructor executes, and therefore affects only one thread. Sometimes in a multi-threaded GuestConfig environment this was causing NullReferenceException in ClearCache() methods where the ThreadStatic filed t_currentImportDscResourceInvocations was accessed.

GuestConfig verified this fix on private binaries.

Side note: the entire section of code, where current fix is, will be removed soon by DSC as a subsystem PR.

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