add handling of xprv argument in consolidateUnspents and fanoutUnspents for those users who don't store an encrypted xprv with us
add handling of xprv argument in consolidateUnspents and fanoutUnspents for those users who don't store an encrypted xprv with us

Summary: Bitstamp is trying to consolidate but can't pass in their xprv

Reviewers: otto, zacleids, kevin, arik, john

Reviewed By: john

Differential Revision: https://phabricator.bitgo.com/D6383

BitGo/bitgo-cli