docker: fix script check execution

In #24095 we made a fix for non-streaming exec into Docker tasks for script
checks and `change_mode = "script"`, but didn't complete E2E testing. We need to
use `ContainerExecAttach` in the new API in order to get stdout/stderr from
tasklets, but the previous `ContainerExecStart` call will prevent this from
running successfully with an error that the exec has already run.

* Ref: [NET-11202 (comment)](https://hashicorp.atlassian.net/browse/NET-11202?focusedCommentId=551618)
* This has shipped in Nomad 1.9.0-beta.1 but not production yet.
* This should fix the remaining issues in nightly E2E for Docker.

drivers/docker/handle.go

@@ -105,17 +105,11 @@ func (h *taskHandle) Exec(ctx context.Context, cmd string, args []string) (*driv
 		Detach: false,
 		Tty:    false,
 	}
-	if err := h.dockerClient.ContainerExecStart(ctx, exec.ID, startOpts); err != nil {
-		return nil, err
-	}
 
 	// hijack exec output streams
-	hijacked, err := h.dockerClient.ContainerExecAttach(ctx, exec.ID, containerapi.ExecStartOptions{
-		Detach: false,
-		Tty:    false,
-	})
+	hijacked, err := h.dockerClient.ContainerExecAttach(ctx, exec.ID, startOpts)
 	if err != nil {
-		return nil, fmt.Errorf("failed to attach to exec: %v", err)
+		return nil, fmt.Errorf("failed to attach to exec object: %w", err)
 	}
 
 	_, err = stdcopy.StdCopy(stdout, stderr, hijacked.Reader)
@@ -128,7 +122,7 @@ func (h *taskHandle) Exec(ctx context.Context, cmd string, args []string) (*driv
 	execResult.Stderr = stderr.Bytes()
 	res, err := h.dockerClient.ContainerExecInspect(ctx, exec.ID)
 	if err != nil {
-		return execResult, err
+		return execResult, fmt.Errorf("failed to inspect exit code of exec object: %w", err)
 	}
 
 	execResult.ExitResult.ExitCode = res.ExitCode

e2e/consul/input/on_update_check_restart.nomad

@@ -48,7 +48,6 @@ job "test" {
         on_update = "ignore_warnings"
 
         args = [
-          "-c",
           "/local/ready.sh"
         ]
 
@@ -95,4 +94,3 @@ EOT
     }
   }
 }
-