packaging: proxy: rename proxy httpd conf.d file

In rhel the mod_proxy_ajp module is loaded in its own conf.d file named
proxy_ajp.conf.

Our proxy configuration should be loaded after this configuration file
to make sure the proxy is loaded and the proxy_ajp_module symbol is
available.

Change-Id: Ic37b672d262985b38ea253c165ae2234d70963d2
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>