Revert "Call FinalizeBlockAndInvalidate without cs_main held"

Summary:
This reverts commit baef60890b540715de692b41cb45a932f5866d45.

This patch's locking is broken.

Test Plan:

make check

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D4946