[WFLY-3255] Fix the value-type description for the SimpleListAttributeDefinition.

Updates the ```value-type``` description for the ```SimpleListAttributeDefition``` from something like
```
"handlers" => {
    "type" => LIST,
    "description" => "The Handlers associated with this Logger.",
    "expressions-allowed" => false,
    "nillable" => true,
    "value-type" => {"handler" => {
        "type" => STRING,
        "description" => "The logging handler.",
        "expressions-allowed" => false,
        "nillable" => true,
        "min-length" => 1L,
        "max-length" => 2147483647L
    }},
    "access-type" => "read-write",
    "storage" => "configuration",
    "restart-required" => "no-services"
}
```
to something like

```
"handlers" => {
    "type" => LIST,
    "description" => "The Handlers associated with this Logger.",
    "expressions-allowed" => false,
    "nillable" => true,
    "value-type" => STRING,
    "access-type" => "read-write",
    "storage" => "configuration",
    "restart-required" => "no-services"
}
```

This affects the following:
* Infinispan
* JGroups
* logging
* domain-management
* server