[token-server] Do not add token utxos for required satoshi inputs

Summary: We need enough XEC to send token txs. We need to make sure we are not using token utxos to get that XEC, otherwise those token utxos will be burned.

Test Plan: npm test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16614