BUG/MINOR: server: Crash when setting FQDN via CLI.

This patch ensures that a DNS resolution may be launched before
setting a server FQDN via the CLI. Especially, it checks that
resolvers was set.

A LEVEL 4 reg testing file is provided.

Thanks to Lukas Tribus for having reported this issue.

Must be backported to 1.8.
2 files changed