Windows packages plugin - Get packages from registry

[sh9189]

Windows packages plugin uses Win32_Product WMI class to get list of installed packages. This causes reconfiguration of all installed windows packages in win2008r2/win2012r2 as per https://support.microsoft.com/en-us/kb/974524, spewing windows event log with 'Package reconfigured messages'. The PR removes the query to Win32_Product WMI class and uses windows registry to get list of all installed packages.
cc @johnbellone

[tas50]

@sh9189 Any chance you can benchmark this? We previously disable the plugin due to the slow performance using WMI. I'm curious if this would allow us to enable this out of the box now.

[sh9189]

Sure, will work on getting some benchmarks for comparison with the previous version.

[sh9189]

@tas50 I did some simple tests on my local PC running windows 7. These are results I see,

	Run 1	Run 2	Run 3	Run 4	Run 5
Use WMI (without packages plugin)	23.070s	21.623s	21.685s	21.882s	23.454s
Use WMI (with packages plugin)	30.919s	30.447s	30.608s	30.608s	30.892s
Use registry (without packages plugin)	23.927s	23.693s	23.329s	23.450s	23.924s
Use registry (with packages plugin)	24.480s	24.504s	24.429ss	24.308s	24.689s

When using WMI to query packages, the packages plugin adds almost 7-8 seconds, but using windows registry to query packages, the packages plugin adds only 0.5-1 second.

I have a pushed a commit to enable packages plugin by default to see how it performs on appveyor.

[sh9189]

On appveyor, I just used start time and end time for bundle exec ohai command to get time taken for ohai. These are results I see,

	Ruby 2.0	Ruby 2.1	Ruby 2.2
Use registry (without packages plugin)	16:20 - 16:38 = 18 seconds	16:09 - 16:25 = 16 seconds	16:14 - 16:30 = 16 seconds
Use registry (with packages plugin)	16:22 - 16:40 = 18 seconds	01:57 - 02:14 = 17 seconds	16:10 - 16:26 = 16 seconds

From the above, it looks like the packages plugin adds almost little to no overhead on appveyor when reading from windows reqistry.

[mcquin]

It looks like this plugin was disabled by default here. Are you intentionally reverting that?

[mcquin]

OK I think I have the proper background on why this plugin was disabled. It seems safe to enable it again. :)

[mcquin]

Code looks great! Can we get some reviews from @chef/client-windows ?

[tas50]

👍

[ksubrama]

👍