tools/memory-model: Make judgelitmus.sh detect hard deadlocks

If a litmus test specifies "Result: Never" and if it contains an
unconditional ("hard") deadlock, then running checklitmus.sh on it will
not flag any errors, despite the fact that there are no executions.
This commit therefore updates judgelitmus.sh to complain about tests
with no executions that are marked, but not as "Result: DEADLOCK".

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>