tools: hv: kvp_daemon: make IPv6-only-injection work

In the case the host only injects an IPv6 address, the dhcp_enabled flag is
true (it's only for IPv4 according to Hyper-V host team), but we still need to
proceed to parse the IPv6 information.

Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-By: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>