Quote variables in the nginx user_data script
Quote variables in the nginx user_data script

elasticsearch_auth has a password in arp1 format, which contains
`$` characters. These are interpreted by bash as variables, so they
get removed from the final string, which makes nginx complain about
password mismatch.

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws