don't free lock name of a named cache

When one uses named cache uWSGI creates a lock for it, but the reference to lock name is lost right after that since ```free()``` is called on it.

Before:

```
$ uwsgi --cache2 name=test_cache,maxitems=1024,blocksize=1024 -s :0 --stats :4444

$ nc localhost 4444
{
        "version":"1.5-dev-37927c6",
[...]
        "locks":[
[...]
                {
                        "����":0
                }
        ],
[...]
```

After

```
$ nc localhost 4444
{
        "version":"1.5-dev-5bbc7ee",
[...]
        "locks":[
[...]
                {
                        "cache_test_cache":1339
                }
        ],
[...]
```

I think it's safe to just don't free that name since it's just allocated once at the start, but You might want to solve this otherwise.