Google-cloud-node: Circle: OS X failures

[stephenplusplus]

Builds are currently failing on OS X:

. scripts/circle/test.sh returned exit code 3

[lukesneeringer]

With a nice and useless error!

[stephenplusplus]

I've disabled OS X testing temporarily.

[stephenplusplus]

It looks like something has changed since I last worked on this. There has only been one switch available to me, "Build OS X project" on https://circleci.com/gh/GoogleCloudPlatform/google-cloud-node/edit#build-environment.

Last I left that page, I set it to "Off". Now, it's "on", but builds are not running on OS X. There is likely more configuration to enable this behind the Org Settings route that I cannot access.