TYP-1555 : Working on trustworthiness / integrity of the twitterriver.

WARNING: At this point we need to renew the "twitter river" it is still
in the process of being removed.
Usually the removal takes approx less than 20 ms
 ... let's wait for 250 milliseconds, before we start a new river, so
we're sure that the old one is removed before we start a new river.