This is one of the bothering issues we had lately in our project. I'm summarizing the list of causes and possible ways to fix / mitigate the same. So what is Apache's Internal Dummy Connection is all about? Official Wiki page explains it better. See snip below,

When the Apache HTTP Server manages its child processes, it needs a way to wake up processes that are listening for new connections. To do this, it sends a simple HTTP request back to itself. This request will appear in the access_log file with the remote address set to the loop-back interface (typically 127.0.0.1 or ::1 if IPv6 is configured). If you log the User-Agent string (as in the combined log format), you will see the server signature followed by "(internal dummy connection)" on non-SSL servers. During certain periods you may see up to one such request for each httpd child process.

#1: VirtualHost

As mentioned, Apache makes a call to itself. If your default VirtualHost is configured to serve dynamic database driven site like Drupal, it will certainly result in increased resource utilization. Changing the same to serve static index.html should make the dummy http request faster and less resource intense. Even if you have directory listing, symbolic links and/or AllowOverriding turned on, it is suggested to disable them.

#2: .htaccess Rewrite Rule

If default VirtualHost couldn't be changed for some reason, with mod_rewrite you can prevent request hitting the Drupal with rewrite rule.