Change first argument of NewWaiter to be able to directly accept RPC
Client and export for external usage.
Refs #3244.
Signed-off-by: Ekaterina Pavlova <ekt@morphbits.io>
If VUB-th block is received, we still can't guaranty that transaction
wasn't accepted to chain. Back this situation by rolling back to a
poll-based waiter.
