mod_cluster requests 503 after httpd is restarted

Issue

mod_cluster works well until I stop the httpd (apache) service. Once the httpd service is started again, we are receiving a 503 error for mod_cluster handled requests. To correct this, I am having to restart the EAP instance. Requests fail on httpd with an error like the following:
```
[error] proxy: CLUSTER: (balancer://mycluster). All workers are in error state
```

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