Do not unpark children of blocks outside of the RPC

Summary:
As per title. When unparking chain automatically, we do not want to unpark all children by default. Only the RPC should do this.

Depends on D2004

Test Plan:

make check
./test/functional/test_runner.py --extended

Reviewers: #bitcoin_abc, jasonbcox, schancel

Reviewed By: #bitcoin_abc, jasonbcox, schancel

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D2057