Mark pub/pub_uploader_test as flaky.

Mark pub/pub_uploader_test as flaky.

Filed http://dartbug.com/7879
Committed: https://code.google.com/p/dart/source/detail?r=17010

[ricow1, 2013-01-14 07:07:07]

TBR

[Bob Nystrom, 2013-01-14 20:30:28]

Thanks for marking this. We'll take a look and try to fix the underlying
problem.

[ahe, 2013-01-15 05:57:48]

lgtm