Existing examples of XML fragments overriding the `defaultValue` element are of the level `leafNode`, for example:
https://github.com/vyos/vyos-1x/blob/current/interface-definitions/interfaces-tunnel.xml.in#L209-L212
```
#include <include/interface/parameters-ttl.xml.i>
<leafNode name="ttl">
<defaultValue>64</defaultValue>
</leafNode>
```
It is useful to generalize this to allow embedded settings:
```
#include <include/accel-ppp/radius-additions.xml.i>
<node name="radius">
<children>
<leafNode name="timeout">
<defaultValue>30</defaultValue>
</leafNode>
<leafNode name="acct-timeout">
<defaultValue>30</defaultValue>
</leafNode>
</children>
</node>
```