Include all views in output of `rndc validation status`

The implementation of rndc validation status iterates over all the views to print their validation status. It takes care to print newlines in between, but it also used put a nul byte at the end of the first view which truncated the output.

After this change, the nul byte is added at the end so that it prints the validation status in all views. The _bind view is skipped because its validation status is irrelevant.