Disable ART run-test 648-many-direct-methods with AOT.

This test sometimes makes dex2oatd timeout on the ART Buildbot:

  --- expected.txt	2017-04-25 05:28:14.630574880 -0700
  +++ output.txt	2017-04-25 06:30:47.355112156 -0700
  @@ -1 +1,3 @@
  -passed
  +dex2oatd F art/runtime/runtime_common.cc] HandleUnexpectedSignal reentered
  +
  +Dex2oat failed.

Ignore these failures on the "optimizing" configurations for now, while
we explore the issue.

Test: Rely on the ART Buildbot
Bug: b/33650497
Change-Id: I7ba34371f88e20b468c0e53f60c406ab8b005634