Consul 1.7.1: no DNS TXT records for Node metadata

Updated from 1.6.2 to 1.7.1 and DNS TXT records for node metadata are gone.

Lets pick one of multiple nodes, name is "p2-02" and it has node metadata attached:
```
addr='http://p2-02.node.consul:8500/v1/agent/self'

curl -s $addr |jq -rM .DebugConfig.NodeMeta
{
"node": "p2-02",
"node-location": "01-R05"
}

curl -s $addr |jq -rM .Meta
{
"consul-network-segment": "",
"node": "p2-02",
"node-location": "01-R05"
}

curl -s $addr |jq -rM .DebugConfig.DNSNodeMetaTXT
true
```

and looking up DNS node TXT RR is ok

```
dig +noall +answer p2-02.node.consul. TXT @consul.service.consul

p2-02.node.consul.TXT"consul-network-segment="
p2-02.node.consul.TXT"node=p2-02"
p2-02.node.consul.TXT"node-location=01-R05"
```

p2-02 runs service "vcs"

```
dig +noall +answer p2-02.vcs.service.consul. A @consul.service.consul
p2-02.vcs.service.dc1.consul. 0 IN A 172.18.107.226
```

but no answer to explicit query

`dig +noall +answer p2-02.vcs.service.consul. TXT @consul.service.consul`

the same is with +all and SRV or ANY.

All server and clients are now (unfortunately) consul version 1.7.1, mixed arm, arm64, amd64 environment (and tested on all arches), OS mainly ubuntu, coreos. Consul DNS is port 53. Consul clients and servers are running in containers.

Same setup and consul version 1.6.2 worked as expected.