* config entry: hardcode proxy-defaults name as global
proxy-defaults can only have the name global. Because of this,
we support not even setting the name in the config file:
```
kind = "proxy-defaults"
```
Previously, writing this would result in the output:
```
Config entry written: proxy-defaults/
```
Now it will output:
```
Config entry written: proxy-defaults/global
```
This change follows what was done for the new Mesh config entry.
Luke Kysow