Pass flags down to GetP2SHSigOpCount and GetSigOpCountWithoutP2SH

Summary:
This will ensure we can use flags to tweak the way sigops are counted in the future. That is necessary for the activation of OP_CHECKDATASIG .

Depends on D1596

Test Plan: Added test cases for the logic change.

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1597