Get the proper serial number for device enrollment.
Get the proper serial number for device enrollment.

BUG=chromium-os:18198
TEST=Enroll a device and check the serial number it sends.


Review URL: http://codereview.chromium.org/7465068

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@94445 0039d316-1c4b-4281-b951-d872f2087c98

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