Temporarily disable the Qt tests added in g58cde5c.

Apparently what works for me doesn't work for the Buildbot users.

Change-Id: I7d3e4f2b89ae8ae3dadc8d92438c0e1923b97ace
Reviewed-on: https://code.wireshark.org/review/4416
Reviewed-by: Gerald Combs <gerald@wireshark.org>