Clean up error handling for the sandbox overlay

contrib/mesos/pkg/minion/server.go

@@ -219,7 +219,7 @@ func (ms *MinionServer) launchHyperkubeServer(server string, args []string, logF
 			}
 			pwd, err := os.Getwd()
 			if err != nil {
-				log.Fatalf("Cannot get current directory: %v", err)
+				panic(fmt.Errorf("Cannot get current directory: %v", err))
 			}
 			kmEnv = append(kmEnv, fmt.Sprintf("%s:%s", e, path.Join(pwd, "bin")))
 		}

contrib/mesos/pkg/scheduler/service/service.go

@@ -366,7 +366,7 @@ func (s *SchedulerServer) prepareExecutorInfo(hks hyperkube.Interface) (*mesos.E
 
 	if s.sandboxOverlay != "" {
 		if _, err := os.Stat(s.sandboxOverlay); os.IsNotExist(err) {
-			log.Fatalf("Sandbox overlay archive not found: %s", s.sandboxOverlay)
+			return nil, nil, fmt.Errorf("Sandbox overlay archive not found: %s", s.sandboxOverlay)
 		}
 		uri, _ := s.serveFrameworkArtifact(s.sandboxOverlay)
 		ci.Uris = append(ci.Uris, &mesos.CommandInfo_URI{Value: proto.String(uri), Executable: proto.Bool(false), Extract: proto.Bool(true)})