qa: Always refresh cache to be out of ibd

Summary:

• qa: Remove mocktime unless required
• qa: Always refresh stale cache to be out of ibd
• qa: Fix wallet_txn_doublespend issue
• test: Simplify create_cache

This is a backport of Core PR15419

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5984