toolTests: change boolean logic.

1. change  should_fail to should_succeed.
2. change
if !should_fail:
    return True
return False

to:
return should_succeed

Change-Id: I6362c94ceee397908b03b5267363091ce892d024
Signed-off-by: Mooli Tayer <mtayer@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34042
Reviewed-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>