Merge pull request #1566 from progrium/1565_mh-fix-nginx-enable

fix logic error in enabling nginx.

plugins/nginx-vhosts/commands

@@ -52,9 +52,9 @@ case "$1" in
     verify_app_name "$2"
     APP="$2"
 
-    if [[ "$(is_app_nginx_enabled $APP)" == "true" ]]; then
-      config_unset --no-restart $APP DOKKU_NO_NGINX
-      unset DOKKU_NO_NGINX
+    if [[ "$(is_app_nginx_enabled $APP)" == "false" ]]; then
+      config_unset --no-restart $APP DOKKU_NO_NGINX NO_VHOST
+      unset DOKKU_NO_NGINX NO_VHOST
       nginx_build_config $APP
     else
       dokku_log_info1 "nginx is already enabled for app ($APP)"