Actually enable the pub update tests.
Actually enable the pub update tests.

Review URL: https://chromiumcodereview.appspot.com//10825142

git-svn-id: a962b240025cf0577aa172e20f49ccb159ba6be1@10669 260f80e4-7a28-3924-810f-c04153c831b5

maxwellpeterson-wf/pub,computmaxer/pub,cjkao/dart-pub,dart-lang/pub,dart-lang/pub