Don't generate operation meta if an operation has already failed

[jonjove]

Description

This is a slight optimization to the way we currently generate meta. I think the new version is also easier to understand. This originally caught my attention because I was wondering why we were generating meta differently prior to protocol version 14.

Checklist

• Reviewed the contributing document
• Rebased on top of master (no merge commits)
• Ran clang-format v5.0.0 (via make format or the Visual Studio extension)
• Compiles
• Ran all tests
• If change impacts performance, include supporting evidence per the performance document

[MonsieurNicolas]

r+ 0b34c8c