fa795cf wallet: Disallow abandon of conflicted txes (MarcoFalke)
Pull request description:
Abandon transactions that are already conflicted is a noop, so don't try and return false/throw instead.
Tree-SHA512: fd2af4149bd2323f7f31fe18685c763790b8589319b4e467b464ab456d5e8971501ab16d124e57a22693666b06ae433ac3e59f0fd6dfbd2be2c6cae8be5bcbd8