fix dns record management when dns host is an IP
fix dns record management when dns host is an IP

Previously we set the string with IP as the list of nameservers.
So, for example, if IP were '172.16.1.1', the list of servers were
['1', '7', '2', '.', '1', '.', '1'] which was clearly falsy.

Now, it's correctly set as ['172.16.1.1'].

Trim/acme-dns-tiny