spindle/engine: run DestroyWorkflow when setup fails

It's possible for SetupWorkflow to provision resources and also fail, so
this makes sense for robustness.

Signed-off-by: Winter <[e-mail]>

spindle/engine/engine.go

···
 					// In the original, we only do in a subset of cases.
 					l.Error("setting up worklow", "wid", wid, "err", err)
 
+					destroyErr := eng.DestroyWorkflow(ctx, wid)
+					if destroyErr != nil {
+						l.Error("failed to destroy workflow after setup failure", "error", destroyErr)
+					}
+
 					dbErr := db.StatusFailed(wid, err.Error(), -1, n)
 					if dbErr != nil {
 						return dbErr