cbuildbot: disable upload_hw_test_artifacts for moblab.
cbuildbot: disable upload_hw_test_artifacts for moblab.

Set upload_hw_test_artifacts to False for stumpy_moblab-release.

BUG=chromium:352707
TEST=trybot run.

Change-Id: I79570bbee385108e91a237b25cc03b6d1378509a
Reviewed-on: https://chromium-review.googlesource.com/190513
Tested-by: Simran Basi <d2a7a6a6d43dd3528f985376c9826504b4136a32@chromium.org>
Reviewed-by: Don Garrett <546ec366615570e68497e3c5df9092106a9808f4@chromium.org>

chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite