When using unbound as DNS proxy, only 3 nameservers get used

[Aminda Suomalainen]

I am using unbound as DNS proxy as documented in `man NetworkManager.conf`, so I also have dnssec-triggerd installed.

When I check my DNS servers I see:

```
% nmcli dev show|grep -i dns
IP4.DNS[1]: 8.8.8.8
IP4.DNS[2]: 172.16.0.1
IP6.DNS[1]: 2001:14ba:f5:1e00::1
```

The first is Google DNS IPv4, the second my router IPv4 and the third my router IPv6 and finally the fourh Google DNS IPv6. But there is no fourth DNS server. NetworkManager only receives three.

```
           unbound: NetworkManager will talk to unbound and dnssec-triggerd,
           providing a "split DNS" configuration with DNSSEC support. The
           /etc/resolv.conf will be managed by dnssec-trigger daemon.

           none: NetworkManager will not modify resolv.conf
```

I believe NetworkManager should receive at least 4 DNS servers as dualstack ISPs usually have two DNS servers or dualstack routers are configured with four. Windows also allows two DNS servers per Internet Protocol.

I think this also applies to dnsmasq and is possibly related to bug #1534055 in glibc.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: network-manager 1.0.4-0ubuntu7
ProcVersionSignature: Ubuntu 4.3.0-5.16-generic 4.3.3
Uname: Linux 4.3.0-5-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.19.3-0ubuntu3
Architecture: amd64
CurrentDesktop: MATE
Date: Thu Jan 14 14:41:06 2016
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2015-12-12 (32 days ago)
InstallationMedia: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Alpha amd64 (20151212)
IpRoute:
 default via 172.16.0.1 dev wlp3s0 proto static metric 600
 169.254.0.0/16 dev wlp3s0 scope link metric 1000
 172.16.0.0/16 dev wlp3s0 proto kernel scope link src 172.16.0.6 metric 600
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
SourcePackage: network-manager
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.NetworkManager.NetworkManager.conf: 2016-01-14T10:55:07.579321
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 wlp3s0 wifi connected /org/freedesktop/NetworkManager/Devices/2 Bahamut_optout_nomap d0a73f1b-5993-4bbf-a2b7-7a0b3e4becf5 /org/freedesktop/NetworkManager/ActiveConnection/0
 enp4s0f1 ethernet unavailable /org/freedesktop/NetworkManager/Devices/0 -- -- --
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/1 -- -- --
nmcli-nm: Error: command ['nmcli', '-f', 'all', 'nm'] failed with exit code 2: Error: Object 'nm' is unknown, try 'nmcli help'.