Close#2956. The failure reason is similar to the one described in #3396
for TestNotary: Blockchain's notificationDispatcher is listening to
block events from storeBlock via separate channel. By the moment single
block addition is finished, notification may or may not be properly
handled by notificationDispatcher, especially given the fact that our
runners are slow. As a result, assert.Eventually with 1-second awaiting
period may fail. This issue is solved by adding one more block, because
the second AddBlock finishes only when it sends block addition event to
notificationDispatcher loop, which means that the previous event was
handled.
Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>
ef3ec190d0