ar: return error from hooks if occured

client/allocrunner/alloc_runner_hooks.go

@@ -249,7 +249,7 @@ func (ar *allocRunner) destroy() error {
 		}
 	}
 
-	return nil
+	return merr.ErrorOrNil()
 }
 
 // shutdownHooks calls graceful shutdown hooks for when the agent is exiting.

client/state/08types.go

@@ -32,7 +32,7 @@ type allocRunnerMutableState08 struct {
 // 0.8.
 //
 // https://github.com/hashicorp/nomad/blob/v0.8.6/client/task_runner.go#L188-L197
-//
+// COMPAT(0.10): Allows upgrading from 0.8.X to 0.9.0.
 type taskRunnerState08 struct {
 	Version            string
 	HandleID           string