improve reliability of two forking unit tests

[spoonincode]

This ports over EOSIO/eos#10356 & EOSIO/eos#10879. The original description from @dimas1185:

This PR fixes 2 flaky parts in nodeos_forked_chain_lr_test and nodeos_short_fork_take_over_lr_test:

1. if node_02 transfer extra block on shutdown, i.e. it was supposed to be killed on block x, but during shutdown it have got x+1 and populated it. For this to be handled correctly, line 434 was removed.
   Example of such failure: https://buildkite.com/EOSIO/eosio/builds/30786#854e0f8f-16e4-4385-81c6-c0d935b1c052
2. need a bit more time to resolve the fork. See line 510. Example of failure: https://buildkite.com/EOSIO/eosio/builds/30805#d6a12c86-b3a9-4efc-b983-2baa24a03e1a
3. Same code changes were added to nodeos_short_fork_take_over_lr_test. Example fail:
   https://buildkite.com/EOSIO/eosio-test-stability/builds/320#2c36f791-7af9-4c4a-ae01-ae75ca6d659f