Taskcluster: start a decision task for all try-* branches
Taskcluster: start a decision task for all try-* branches

This is an alternative fix for https://github.com/servo/saltfs/issues/903,
and anticipates adding trychooser support to Taskcluster

paulrouget/servo,szeged/servo,nnethercote/servo,KiChjang/servo,szeged/servo,szeged/servo,larsbergstrom/servo,KiChjang/servo,larsbergstrom/servo,larsbergstrom/servo,notriddle/servo,szeged/servo,peterjoel/servo,splav/servo,DominoTree/servo,nnethercote/servo,larsbergstrom/servo,emilio/servo,splav/servo,paulrouget/servo,splav/servo,saneyuki/servo,szeged/servo,nnethercote/servo,paulrouget/servo,peterjoel/servo,emilio/servo,KiChjang/servo,larsbergstrom/servo,splav/servo,DominoTree/servo,szeged/servo,peterjoel/servo,splav/servo,peterjoel/servo,paulrouget/servo,emilio/servo,DominoTree/servo,paulrouget/servo,paulrouget/servo,saneyuki/servo,peterjoel/servo,saneyuki/servo,splav/servo,KiChjang/servo,notriddle/servo,szeged/servo,notriddle/servo,notriddle/servo,emilio/servo,saneyuki/servo,DominoTree/servo,KiChjang/servo,pyfisch/servo,DominoTree/servo,emilio/servo,DominoTree/servo,paulrouget/servo,larsbergstrom/servo,DominoTree/servo,peterjoel/servo,nnethercote/servo,szeged/servo,notriddle/servo,splav/servo,pyfisch/servo,pyfisch/servo,nnethercote/servo,szeged/servo,notriddle/servo,pyfisch/servo,splav/servo,nnethercote/servo,saneyuki/servo,larsbergstrom/servo,nnethercote/servo,saneyuki/servo,pyfisch/servo,paulrouget/servo,emilio/servo,larsbergstrom/servo,notriddle/servo,emilio/servo,pyfisch/servo,emilio/servo,KiChjang/servo,pyfisch/servo,saneyuki/servo,pyfisch/servo,KiChjang/servo,splav/servo,DominoTree/servo,notriddle/servo,paulrouget/servo,larsbergstrom/servo,KiChjang/servo,nnethercote/servo,DominoTree/servo,pyfisch/servo,paulrouget/servo,saneyuki/servo,peterjoel/servo,saneyuki/servo,nnethercote/servo,peterjoel/servo,KiChjang/servo,notriddle/servo,pyfisch/servo,emilio/servo,szeged/servo,emilio/servo,peterjoel/servo,nnethercote/servo,notriddle/servo,saneyuki/servo,KiChjang/servo,splav/servo,DominoTree/servo,peterjoel/servo,larsbergstrom/servo