fa2e038 test: Fix extra_args in wallet_import_rescan.py (MarcoFalke)

Pull request description:

  Bug introduced by me (:man_facepalming:) in fa25668

  For reference:

  ```
  >>> a = [[]]*2
  >>> a[0] += ['ONE']
  >>> a
  [['ONE'], ['ONE']]

  >>> a = [[] for _ in range(2)]
  >>> a[0] += ['ONE']
  >>> a
  [['ONE'], []]

ACKs for top commit:
  theStack:
    utACK fa2e038

Tree-SHA512: 7d75a0d06233d013d62198ea95793612242254d5d90f393d01b2beef5abc78d6e85c796532311638f16cfed3b66a7ae41a108c0fe6f0f5d7f6616b042c670df7

Summary:
The initial commit added tests that are not relevant for us,
but also did some minor refactoring that could add more robustness
if the tests evolve in the future (remember `extra_args` in
`setup_network` in nodes are restarted).

The initial commit introduced a bug later fixed in [[bitcoin/bitcoin#16920 | PR16920]].
This fix taken into accound here.

This concludes backport of Core [[bitcoin/bitcoin#16465 | PR16465]] - part 3 of 3
Commit bitcoin/bitcoin@fa25668
Depends on D8055

Test Plan: `ninja && test/functional/test_runner.py wallet_import_rescan.py`

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D8056