miscTests: mark testValidInput as broken

As reported in http://gerrit.ovirt.org/27959, we can no longer read
arbitrary lengths with O_DIRECT. Backporting the the proper solution
from master would take more time that I care to spend on this right now.

Change-Id: If026543a6a2bb8da40af4541ae6fe4c3e94b5219
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29786
Reviewed-by: Sandro Bonazzola <sbonazzo@redhat.com>
Reviewed-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-by: Nir Soffer <nsoffer@redhat.com>