stop metadata.mds service if running in osx

[vigneshsarma]

for issue #445

@aneeshusa creating the PR, to see the tests run.

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This change is

[aneeshusa]

Thanks for the PR! The commit itself looks great, so here is some review to improve the commit message (see also):

Title:

• Start with a capital letter
• stop -> Disable
• metadata.mds -> metadata indexing service
• if running in osx -> on OS X

Body:

• Instead of for issue #445, please include the actual reasoning for this commit from the issue. Why is this commit being made? What problem does it solve? Include details from the IRC convo linked in the commit. (The goal is to have the body by itself include the relevant details so it is useful offline, e.g. in git log.)

[vigneshsarma]

@aneeshusa What do you think now?

I am no good at writing these kind of stuff. Hope its ok 😄

[aneeshusa]

This is better but there's still room for improvement:

• Good that you included info from IRC about CPU usage, but let's be even more specific: "taking 100% of a CPU" is a quote that has an illustrative statistic
• Make sure to use complete sentences

If you're having trouble with the wording, you can also give me access to push to your branch with some suggestions.

[bors-servo]

☔ The latest upstream changes (presumably #483) made this pull request unmergeable. Please resolve the merge conflicts.