Clarify & correct require_valid_user setting

Fixes COUCHDB-3100

rel/overlay/etc/default.ini

@@ -42,11 +42,13 @@ n=3
 ; placement = metro-dc-a:2,metro-dc-b:1
 
 [chttpd]
+; These settings affect the main, clustered port (5984 by default).
 port = {{cluster_port}}
 bind_address = 127.0.0.1
 backlog = 512
 docroot = {{fauxton_root}}
 socket_options = [{recbuf, 262144}, {sndbuf, 262144}, {nodelay, true}]
+require_valid_user = false
 
 [database_compaction]
 ; larger buffer sizes can originate smaller files
@@ -135,6 +137,8 @@ port = 6984
 ; min_writer_size = 16777216
 
 [couch_httpd_auth]
+; WARNING! This only affects the node-local port (5986 by default).
+; You probably want the settings under [chttpd].
 authentication_db = _users
 authentication_redirect = /_utils/session.html
 require_valid_user = false