addzone fails with "no matching view found for '_default'" for bind9 with multi-view config

[Andreas F. Bobak]

Our bind9 configuration uses multiple views, which seems to disable the "_default" view.

There doesn't seem to be a way to specify the view for the `rndc addzone` command, this makes the designate-worker fail with in our setup:

```
designate-worker.log:Stderr: "sudo: setrlimit(RLIMIT_CORE): Operation not permitted\nrndc: 'addzone' failed: not found\nno matching view found for '_default'\n".
```

Executing the command manually:

```
rndc -s 10.0.0.xx -p 953 -k /etc/designate/rndc_10_0_0_xx.key addzone cloud.example.com '{ type slave; masters { 10.0.0.yy port 5354;}; file "slave.cloud.example.com.6a126118-293c-4a96-9888-d2b5bef420da"; };'
```

gives the same output:
```
rndc: 'addzone' failed: not found
no matching view found for '_default'
```

Adding an existing view different from "_default" executes the command just fine:

```
rndc -s 10.0.0.xx -p 953 -k /etc/designate/rndc_10_0_0_xx.key addzone cloud.example.com in example-view '{ type slave; masters { 10.0.0.yy port 5354;}; file "slave.cloud.example.com.6a126118-293c-4a96-9888-d2b5bef420da"; };'
```