[terraform] Error when configuring against external PostgreSQL over IPv6

When attempting to configure an external postgresql database using an IPv6 connection like this:

postgresql['vip'] = "2600:1f1c:885:dead:beef:1234:abcd:a1b2"

The following error is logged:

2019-12-11 17:35:49 =ERROR REPORT====

pool 'sqerl' failed to start member: {error,{{bad_host,"2600:1f1c:885:fd01:ff85:8086:247f:6f67"},[{envy_parse,maybe_parse,3,[{file,"/var/cache/omnibus/chef-server/src/oc_erchef/_build/default/lib/envy/src/envy_pars
e.erl"},{line,43}]},{chef_secrets_sqerl,config,1,[{file,"/var/cache/omnibus/chef-server/src/oc_erchef/_build/default/lib/chef_secrets/src/chef_secrets_sqerl.erl"},{line,18}]},{sqerl_client,init,1,[{file,"/var/cache
/omnibus/chef-server/src/oc_erchef/_build/default/lib/sqerl/src/sqerl_client.erl"},{line,124}]},{gen_server,init_it,2,[{file,"gen_server.erl"},{line,365}]},{gen_server,init_it,6,[{file,"gen_server.erl"},{line,333}]
},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,247}]}]}}

Interestingly, if you attempt to use an IPv6 FQDN like this:

postgresql['vip'] = "postgresql.internal"

A similar error is logged:

2019-12-11 17:16:10 =ERROR REPORT====

pool 'sqerl' failed to start member: {error,{{bad_host,"postgresql.internal"},[{envy_parse,maybe_parse,3,[{file,"/var/cache/omnibus/chef-server/src/oc_erchef/_build/default/lib/envy/src/envy_parse.erl"},{line,43}]}
,{chef_secrets_sqerl,config,1,[{file,"/var/cache/omnibus/chef-server/src/oc_erchef/_build/default/lib/chef_secrets/src/chef_secrets_sqerl.erl"},{line,18}]},{sqerl_client,init,1,[{file,"/var/cache/omnibus/chef-serve
r/src/oc_erchef/_build/default/lib/sqerl/src/sqerl_client.erl"},{line,124}]},{gen_server,init_it,2,[{file,"gen_server.erl"},{line,365}]},{gen_server,init_it,6,[{file,"gen_server.erl"},{line,333}]},{proc_lib,init_p_
do_apply,3,[{file,"proc_lib.erl"},{line,247}]}]}}

Reproduce the failure with the postgresql['vip'] IPv6 literal and FQDN examples. Trace the reported path through envy_parse.erl, chef_secrets_sqerl.erl, and sqerl_client.erl, starting at the envy_parse call; done means external PostgreSQL configuration accepts the IPv6 cases without a bad_host error.