add GPU neural ODE test

Author: ChrisRackauckas

test/runtests.jl

@@ -21,6 +21,10 @@ end
 if !is_APPVEYOR && GROUP == "Downstream"
     activate_downstream_env()
     Pkg.test("DiffEqFlux")
+end
+
+if !is_APPVEYOR && GROUP == "Downstream"
+    activate_downstream_env()
     @safetestset "DiffEqFlux GPU" begin include("gpu_neural_ode.jl") end
 end
 end