Better alignment of MetronomeMark to MultiMeasureRest (issue 6972044)

[k-ohara5a5a]

See https://codereview.appspot.com/1579041#msg3

I'm not sure Neil is correct in his comment, but it would be cleaner to
modify the code that responded to Neil's suggestion, rather than prevent
it from taking effect downstream.


https://codereview.appspot.com/6972044/diff/1/lily/metronome-engraver.cc
File lily/metronome-engraver.cc (right):

https://codereview.appspot.com/6972044/diff/1/lily/metronome-engraver.cc#newcode134
lily/metronome-engraver.cc:134: has_note_column_ = true;
Why not just
\override Score.MetronomeMark #'non-break-align-symbols =
#'(note-column-interface   multi-measure-rest-interface)

https://codereview.appspot.com/6972044/