Code review comment for lp:~alan-griffiths/mir/fix-1284597

mir::raii::paired_calls is cryptic, but then one could argue RAII and C++ itself is equally so by design. So that's just an opinion.

Also, from memory mg::BufferInitializer only exists to support examples/*. Last time I looked into it, that class had no purpose in the rest of Mir. It's probably a bad idea to make extensive use of such classes which are only used in examples/* and will never be used in real servers/clients.