Allow Multivalue TXT Records

[esinx]

Related to DNS Challenges being rejected because certbot cannot add multivalue TXT records to Route 53.

Motivation

Currently, when K8s want to reissue certificates, in order for the certificate request to complete, it must go through an order to complete an acme challenge.

To complete this challenge, it needs to have access to add another TXT record to Route 53. However, doing so when there already exists non-multivalue TXT records leads to the following error:

failed to change Route 53 record set: InvalidChangeBatch: [RRSet with DNS name _acme-challenge.[DOMAIN NAME], 
type TXT, SetIdentifier "(redacted)" cannot be created because a non multivalue answer
rrset exists with the same name and type.[]

Changes

This PR ensures the records created by terraform to Route53 are multivalue records.

[joyliu-q]

LGTM