Clear the IFP bip in the version by default to avoid accidental activation

Summary: While the defautl behavior of BIP9 is to vote yes by default, it is preferable to avoid doing so accidentaly.

Test Plan:

make check
./test/functional/test_runner.py

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5305