Fix a test failure I observed on ent re cluster listener (#8647)
Fix a test failure I observed on ent re cluster listener (#8647)

Panics when the cluster listener changes while we're setting up request forwarding.

rnaveiras/vault,rnaveiras/vault,rnaveiras/vault,hashicorp/vault,rnaveiras/vault,hartsock/vault,hashicorp/vault,hartsock/vault,hashicorp/vault,hashicorp/vault,hartsock/vault,hashicorp/vault,hashicorp/vault,hartsock/vault,hartsock/vault,rnaveiras/vault