fix PercentTimeinGC metric

[trunov-ms]

Fix bug for counting value PercentTimeinGC

From program WEBMTest.exe in class Win32_PerfRawData_NETFramework_NETCLRMemory I was found counter type

[DisplayName("% Time in GC"): ToInstance, countertype(537003008): ToInstance, 
perfindex(2606): ToInstance, helpindex(2607): ToInstance, defaultscale(0): ToInstance, 
perfdetail(100): ToInstance] uint32 PercentTimeinGC

The mapping for countertype(537003008) is PERF_RAW_FRACTION.

For Cooking Type MSDN has formula (100 * CounterValue) / BaseValue
Article

[breed808]

Hi there, thanks for submitting this and a big apology for not reviewing sooner! I must have accidentally hit "read" on the notification for this pull request and subsequently missed it.

I've left a couple minor comments, let me know if any info is needed.

[breed808]

Thanks for making those amendments. The file needs to be formatted with gofmt in order to pass CI.
Once that's done we can merge the changes.