Unable to pass the credentials to docker inside docker

**What happened**:
M running a pod with a service account(annotated with a role). Inside the pods these environment variables are mounted :

AWS_WEB_IDENTITY_TOKEN_FILE
AWS_REGION
AWS_ROLE_ARN

inside the pod, when m trying to run a docker command like this :

```bash
docker run --rm \
-e AWS_WEB_IDENTITY_TOKEN_FILE \
-e AWS_REGION \
-e AWS_ROLE_ARN \
-v "/var/run/secrets/eks.amazonaws.com/serviceaccount/token:/var/run/secrets/eks.amazonaws.com/serviceaccount/token" \
node:10.13-alpine \
sh -c "sls deploy"
```

it is unable to use this credentials, looks like this path can't be mounted corretly:

`/var/run/secrets/eks.amazonaws.com/serviceaccount/token`

**What you expected to happen**:
docker command on the pod should run successfully.

**How to reproduce it (as minimally and precisely as possible)**:
Follow [this](https://docs.aws.amazon.com/eks/latest/userguide/specify-service-account-role.html) to setup EKS IAM service account and then run the above docker run command.

**Anything else we need to know?**:

**Environment**:
- AWS Region: `ap-southeast-1`
- EKS Platform version (if using EKS, run `aws eks describe-cluster --name --query cluster.platformVersion`): `eks.9`
- Kubernetes version (if using EKS, run `aws eks describe-cluster --name --query cluster.version`): `1.14`
- Webhook Version:

Reproduce the report by following the linked EKS IAM service-account setup and running the provided docker command in a pod. Start by checking how the webhook-mounted token path behaves across the pod and nested Docker container; done means the nested command can use the service-account credentials and `sls deploy` completes successfully.

Written by the indexing model from the issue text.