test: fix status check in replication/transaction

On heavy loaded hosts found the following issue:

  [046] --- replication/transaction.result	Wed Sep 30 17:19:32 2020
  [046] +++ /tmp/tnt/rejects/replication/transaction.reject	Tue Nov 24 04:39:29 2020
  [046] @@ -234,7 +234,7 @@
  [046]  ...
  [046]  box.info.replication[1].upstream.status
  [046]  ---
  [046] -- follow
  [046] +- disconnected
  [046]  ...
  [046]  test_run:cmd("switch default")
  [046]  ---
  [046]

It happened because box.cfg was not ready to provide information. In
real there is no need to use local check for replication information
parts availablity, due to wait_upstream() function used below, do it
itself.

Closes #5563
Closes tarantool/tarantool-qa#35