Merge #9977: QA: getblocktemplate_longpoll.py should always use >0 fee tx

Summary:
655df06 QA: getblocktemplate_longpoll.py should always use >0 fee tx (Suhas Daftuar)

Tree-SHA512: 016647ba1408f8aaa3fc954835542354d54bf2391c4252c1c505101edbbe1cf8dd6a07060930109d0341f86360b9391dfef439999a93a5bae68fc901dace0b71

Backport of Core PR9977
https://github.com/bitcoin/bitcoin/pull/9977/files

Test Plan:

test_runner.py mining_getblocktemplate_longpoll

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D3218