Fix PubSub for logs when using light client :

prior to this fix the pubsub process did send a
query for each new block header (and for each subs : there is something
to optimize here) by setting from and to of the filter at this block
number; but there was a bug in the code that fetch logs : it was non
inclusive for its start bound, meaning that with start bound = end bound
we never query any block (and attached logs).