web: Do not depend IP address of app

web/docker-entry.sh

@@ -1,5 +1,4 @@
 #!/bin/bash
 echo Starting Nginx
-sed -Ei "s/PLATFORM_ADDR/$PLATFORM_PORT_80_TCP_ADDR/" /etc/nginx/sites-available/mattermost
 sed -Ei "s/PLATFORM_PORT/$PLATFORM_PORT_80_TCP_PORT/" /etc/nginx/sites-available/mattermost
 nginx -g 'daemon off;'

web/mattermost

@@ -30,7 +30,7 @@ server {
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Forwarded-Proto $scheme;
         proxy_set_header   X-Frame-Options   SAMEORIGIN;
-        proxy_pass http://PLATFORM_ADDR:PLATFORM_PORT;
+        proxy_pass http://app:PLATFORM_PORT;
     }
 }