1. Proposed title of this feature request
Given that config
```
ipv6:
enabled: true
autoconf: true
dhcp: true
auto-dns: false
auto-gateway: true
auto-routes: true

```
there is this error
```
failed to execute 'nmstatectl gc', error: Autoconf without DHCP is not supported yet
```
this seems technically incorrect because autconf== allows the IP autoconfiguration from RAs, while you do not want the dhcp (an IP coming from a DHCPv6 server that might exist)

2. What is the nature and description of the request?

3. Why does the customer need this? (List the business requirements here)
There are partners doing IPv6 with SLAAC and no DHCP and that is confusing (and unknown if there is a real impact)

4. List any affected packages or components.
nmstate (ctl)