disable Trace.java test when running on Travis-CI
disable Trace.java test when running on Travis-CI

Trace.java fails randomly on Travis, but we've never been able to
reproduce or debug the failure elsewhere, so now we skip it if we
detect the suite is running on Travis.

lwahlmeier/avian,lwahlmeier/avian,MaartenR/avian,dicej/avian,lwahlmeier/avian,dicej/avian,MaartenR/avian,lwahlmeier/avian,dicej/avian,MaartenR/avian,MaartenR/avian,dicej/avian