After migrating to get_config_dict() the following configuration no longer works:
```
set service router-advert interface eth0 default-lifetime '1800'
set service router-advert interface eth0 default-preference 'high'
set service router-advert interface eth0 hop-limit '64'
set service router-advert interface eth0 interval max '30'
set service router-advert interface eth0 link-mtu '1500'
set service router-advert interface eth0 name-server '2001:db8:200::1'
set service router-advert interface eth0 name-server '2001:db8:200::2'
set service router-advert interface eth0 prefix 2001:db8:200:50::/64 valid-lifetime 'infinity'
set service router-advert interface eth0 reachable-time '0'
set service router-advert interface eth0 retrans-timer '0'
```
It used to work in VyOS 1.3-rolling-202006150117