Make ServoLayoutNode::debug_id() less convoluted.
Make ServoLayoutNode::debug_id() less convoluted.

CJ8664/servo,nrc/servo,mbrubeck/servo,CJ8664/servo,jimberlage/servo,dsandeephegde/servo,peterjoel/servo,thiagopnts/servo,jimberlage/servo,larsbergstrom/servo,notriddle/servo,ConnorGBrewster/servo,emilio/servo,KiChjang/servo,anthgur/servo,pyfisch/servo,CJ8664/servo,paulrouget/servo,splav/servo,cbrewster/servo,splav/servo,ConnorGBrewster/servo,canaltinova/servo,canaltinova/servo,peterjoel/servo,fiji-flo/servo,ConnorGBrewster/servo,avadacatavra/servo,paulrouget/servo,canaltinova/servo,larsbergstrom/servo,ConnorGBrewster/servo,fiji-flo/servo,splav/servo,rnestler/servo,sadmansk/servo,saneyuki/servo,nrc/servo,mattnenterprise/servo,peterjoel/servo,mbrubeck/servo,nnethercote/servo,cbrewster/servo,jimberlage/servo,dati91/servo,peterjoel/servo,rnestler/servo,canaltinova/servo,saneyuki/servo,larsbergstrom/servo,saneyuki/servo,dati91/servo,avadacatavra/servo,nrc/servo,upsuper/servo,DominoTree/servo,rnestler/servo,notriddle/servo,szeged/servo,CJ8664/servo,szeged/servo,cbrewster/servo,dsandeephegde/servo,sadmansk/servo,upsuper/servo,cbrewster/servo,pyfisch/servo,notriddle/servo,dati91/servo,DominoTree/servo,emilio/servo,peterjoel/servo,thiagopnts/servo,sadmansk/servo,KiChjang/servo,jimberlage/servo,notriddle/servo,KiChjang/servo,fiji-flo/servo,pyfisch/servo,szeged/servo,peterjoel/servo,upsuper/servo,paulrouget/servo,upsuper/servo,anthgur/servo,cbrewster/servo,szeged/servo,eddyb/servo,mbrubeck/servo,canaltinova/servo,KiChjang/servo,notriddle/servo,larsbergstrom/servo,splav/servo,sadmansk/servo,saneyuki/servo,notriddle/servo,emilio/servo,dati91/servo,mattnenterprise/servo,jimberlage/servo,notriddle/servo,nrc/servo,DominoTree/servo,anthgur/servo,dati91/servo,peterjoel/servo,eddyb/servo,saneyuki/servo,fiji-flo/servo,thiagopnts/servo,rnestler/servo,sadmansk/servo,sadmansk/servo,pyfisch/servo,eddyb/servo,saneyuki/servo,peterjoel/servo,saneyuki/servo,nnethercote/servo,nnethercote/servo,larsbergstrom/servo,emilio/servo,szeged/servo,thiagopnts/servo,rnestler/servo,KiChjang/servo,DominoTree/servo,fiji-flo/servo,nrc/servo,DominoTree/servo,DominoTree/servo,ConnorGBrewster/servo,mattnenterprise/servo,dati91/servo,dati91/servo,avadacatavra/servo,pyfisch/servo,notriddle/servo,KiChjang/servo,CJ8664/servo,paulrouget/servo,cbrewster/servo,anthgur/servo,eddyb/servo,upsuper/servo,paulrouget/servo,mbrubeck/servo,mattnenterprise/servo,szeged/servo,emilio/servo,CJ8664/servo,SimonSapin/servo,mbrubeck/servo,cbrewster/servo,splav/servo,rnestler/servo,splav/servo,DominoTree/servo,saneyuki/servo,peterjoel/servo,cbrewster/servo,SimonSapin/servo,mattnenterprise/servo,fiji-flo/servo,szeged/servo,mattnenterprise/servo,dsandeephegde/servo,jimberlage/servo,emilio/servo,canaltinova/servo,notriddle/servo,CJ8664/servo,SimonSapin/servo,thiagopnts/servo,nnethercote/servo,mbrubeck/servo,DominoTree/servo,KiChjang/servo,emilio/servo,nnethercote/servo,szeged/servo,szeged/servo,dsandeephegde/servo,pyfisch/servo,anthgur/servo,paulrouget/servo,emilio/servo,anthgur/servo,splav/servo,dsandeephegde/servo,rnestler/servo,mattnenterprise/servo,larsbergstrom/servo,nnethercote/servo,dsandeephegde/servo,avadacatavra/servo,jimberlage/servo,mattnenterprise/servo,avadacatavra/servo,paulrouget/servo,thiagopnts/servo,larsbergstrom/servo,upsuper/servo,eddyb/servo,sadmansk/servo,KiChjang/servo,thiagopnts/servo,upsuper/servo,CJ8664/servo,nrc/servo,nnethercote/servo,KiChjang/servo,rnestler/servo,dsandeephegde/servo,larsbergstrom/servo,emilio/servo,SimonSapin/servo,larsbergstrom/servo,SimonSapin/servo,pyfisch/servo,splav/servo,peterjoel/servo,ConnorGBrewster/servo,anthgur/servo,dsandeephegde/servo,upsuper/servo,SimonSapin/servo,saneyuki/servo,nnethercote/servo,mbrubeck/servo,sadmansk/servo,jimberlage/servo,DominoTree/servo,paulrouget/servo,jimberlage/servo,avadacatavra/servo,dati91/servo,nrc/servo,splav/servo,larsbergstrom/servo,splav/servo,eddyb/servo,avadacatavra/servo,DominoTree/servo,eddyb/servo,saneyuki/servo,fiji-flo/servo,eddyb/servo,SimonSapin/servo,pyfisch/servo,thiagopnts/servo,avadacatavra/servo,anthgur/servo,canaltinova/servo,SimonSapin/servo,pyfisch/servo,paulrouget/servo,szeged/servo,ConnorGBrewster/servo,fiji-flo/servo,nnethercote/servo,KiChjang/servo,emilio/servo,paulrouget/servo,notriddle/servo,mbrubeck/servo,canaltinova/servo,ConnorGBrewster/servo,nnethercote/servo,pyfisch/servo