Remove some more references to localhost

Continuation of 1f0cc92b33.

As an explanation for the problem:
when saying `localhost` on the host, it sometimes gets resolved to `::1`
and sometimes to `127.0.0.1`. On the unfortunate occassions that
it gets resolved to `::1`, the container won't be able to serve the
request, because Docker containers don't have IPv6 enabled by default.

To avoid this problem, we simply prevent any lookups from happening
and explicitly use `127.0.0.1`.

examples/apache/matrix-riot-web.conf

@@ -10,7 +10,7 @@
 		ProxyPreserveHost On
 		ProxyRequests Off
 		ProxyVia On
-		ProxyPass http://localhost:2402/.well-known/acme-challenge
+		ProxyPass http://127.0.0.1:2402/.well-known/acme-challenge
 	</Location>
 
 	Redirect permanent / https://riot.DOMAIN/
@@ -33,8 +33,8 @@
 	ProxyRequests Off
 	ProxyVia On
 
-	ProxyPass / http://localhost:8765/
-	ProxyPassReverse / http://localhost:8765/
+	ProxyPass / http://127.0.0.1:8765/
+	ProxyPassReverse / http://127.0.0.1:8765/
 
 	ErrorLog ${APACHE_LOG_DIR}/riot.DOMAIN-error.log
 	CustomLog ${APACHE_LOG_DIR}/riot.DOMAIN-access.log combined

examples/apache/matrix-synapse.conf

@@ -9,7 +9,7 @@
 		ProxyPreserveHost On
 		ProxyRequests Off
 		ProxyVia On
-		ProxyPass http://localhost:2402/.well-known/acme-challenge
+		ProxyPass http://127.0.0.1:2402/.well-known/acme-challenge
 	</Location>
 
 	Redirect permanent / https://matrix.DOMAIN/
@@ -38,8 +38,8 @@
 	ProxyPassMatch ^/_matrix/client/r0/user_directory/search !
 
 	# Proxy all remaining traffic to Synapse
-	ProxyPass / http://localhost:8008/
-	ProxyPassReverse / http://localhost:8008/
+	ProxyPass / http://127.0.0.1:8008/
+	ProxyPassReverse / http://127.0.0.1:8008/
 
 	# Map /.well-known/matrix/client for client discovery
 	Alias /.well-known/matrix/client /matrix/static-files/.well-known/matrix/client
@@ -60,12 +60,12 @@
 
 	# Map /_matrix/identity to the identity server
 	<Location /_matrix/identity>
-		ProxyPass http://localhost:8090/_matrix/identity
+		ProxyPass http://127.0.0.1:8090/_matrix/identity
 	</Location>
 
 	# Map /_matrix/client/r0/user_directory/search to the identity server
 	<Location /_matrix/client/r0/user_directory/search>
-		ProxyPass http://localhost:8090/_matrix/client/r0/user_directory/search
+		ProxyPass http://127.0.0.1:8090/_matrix/client/r0/user_directory/search
 	</Location>
 
 	ErrorLog ${APACHE_LOG_DIR}/matrix.DOMAIN-error.log

roles/matrix-nginx-proxy/templates/usr-local-bin/matrix-ssl-lets-encrypt-certificates-renew.j2

@@ -4,7 +4,7 @@
 # need to forward requests for `/.well-known/acme-challenge` to the certbot container.
 #
 # This can happen inside the container network by proxying to `http://matrix-certbot:8080`
-# or outside (on the host) by proxying to `http://localhost:{{ matrix_ssl_lets_encrypt_certbot_standalone_http_port }}`.
+# or outside (on the host) by proxying to `http://127.0.0.1:{{ matrix_ssl_lets_encrypt_certbot_standalone_http_port }}`.
 
 docker run \
 	--rm \