Pass config down to AcceptToMemoryPoolWorker

Summary: We want to have it available to do contextual checks on transactions.

Test Plan:

make check

Reviewers: freetrader, sickpig, #bitcoin_abc, kyuupichan

Reviewed By: #bitcoin_abc, kyuupichan

Subscribers: kyuupichan

Differential Revision: https://reviews.bitcoinabc.org/D141