The network configuration for configdrive2 is in the format of
/etc/network/interfaces, where the DNS settings are configured with the
'dns-nameservers' and 'dns-search' options in an interface stanza.
But they were written with an underscore instead of a dash, and right
after the stanza of the loopback interface, so cloud-init ignored them
and the configured nameservers and search domains never ended up in the
guest. Just using the correct option names would not be enough, as
cloud-init does not apply the DNS settings of the loopback interface
when rendering the configuration with netplan, for example.
Write the options with a dash and add them to the stanzas of the
statically configured interfaces, like it is already done for the
cloudbase-init configuration.
Signed-off-by: Michal Fox <me@dualfroz.com>