Add SCRIPT_ENABLE_SIGHASH_FORKID to the CheckInputs sanity check in AcceptToMemoryPoolWorker

Summary: This sanity check will reject BIP143 txns if this flag isn't passed.

Test Plan: Right now the activation code isn't ready, so the check is unrecheable.

Reviewers: freetrader, awemany, sickpig, kyuupichan, #bitcoin_abc

Reviewed By: freetrader, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D186