[pyauto] Ignore policy test import errors
[pyauto] Ignore policy test import errors

policy protobuf import errors is causing failure in running any pyauto test on chromeos.
Temporarily ignore the import errors.

TBR=frankf@chromium.org
R=frankf@chromium.org
BUG=chromium-os:26220
TEST=

Review URL: https://chromiumcodereview.appspot.com/9385036

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@121649 0039d316-1c4b-4281-b951-d872f2087c98

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