Updating nginx docs for clarity (#2561)

* Update nginx docs

Added step to remove passphrase from self-signed cert private key.
Removed http block since enabled sites now are included inside the http block in modern nginx configs

* Update nginx.markdown

Added note about sites-available directory in RPM-based distros (and possibly others)

source/_docs/ecosystem/nginx.markdown

@@ -40,6 +40,7 @@ If you do not own your own domain, you may generate a self-signed certificate. T
 
 ```
 openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 9999
+openssl rsa -in key.pem -out key.pem
 sudo cp key.pem cert.pem /etc/nginx/ssl
 sudo chmod 600 /etc/nginx/ssl/key.pem /etc/nginx/ssl/cert.pem
 sudo chown root:root /etc/nginx/ssl/key.pem /etc/nginx/ssl/cert.pem
@@ -58,6 +59,10 @@ sudo openssl dhparam -out dhparams.pem 2048
 
 Create a new file `/etc/nginx/sites-available/hass` and copy the configuration file at the bottom of the page into it.
 
+<p class='note'>
+Some Linux distributions (including CentOS and Fedora) will not have the `/etc/nginx/sites-available/` directory. In this case, remove the default server {} block from the `/etc/nginx/nginx.conf` file and paste the contents from the bottom of the page in its place. If doing this, proceed to step 7.
+</p>
+
 ### {% linkable_title 6. Enable the Home Assistant configuration. %}
 
 ```
@@ -78,22 +83,21 @@ Forward ports 443 and 80 to your server on your router. Do not forward port 8123
 ### {% linkable_title NGINX Config %}
 
 ```
-http {
-    map $http_upgrade $connection_upgrade {
+map $http_upgrade $connection_upgrade {
     default upgrade;
     ''      close;
-    }
+}
 
-    server {
+server {
     # Update this line to be your domain
     server_name example.com;
 
     # These shouldn't need to be changed
     listen [::]:80 default_server ipv6only=off;
     return 301 https://$host$request_uri;
-    }
+}
 
-    server {
+server {
     # Update this line to be your domain
     server_name example.com;
 
@@ -128,6 +132,5 @@ http {
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection $connection_upgrade;
     }
-    }
 }
 ```