Disable KeepAlive on proxies

Disable KeepAlive to fix bug #1630664 a.k.a the
('Connection aborted.', BadStatusLine("''",)) error

Change-Id: I7f267e247338a9b8fff0fd17c8eba9406786af70
Related-Prod: PROD-20041
diff --git a/apache/files/proxy.conf b/apache/files/proxy.conf
index baad919..b48ccce 100644
--- a/apache/files/proxy.conf
+++ b/apache/files/proxy.conf
@@ -6,6 +6,7 @@
   {%- include "apache/files/_name.conf" %}
   {%- include "apache/files/_ssl.conf" %}
   {%- include "apache/files/_log.conf" %}
+  {%- include "apache/files/_core.conf" %}
 
   DocumentRoot /var/www