Changed graphite site file name in apache

According to apache2 cookbook (https://github.com/onehealth-cookbooks/apache2/blob/master/templates/default/apache2.conf.erb#L268) , site file name should have  .conf file-ext.

<% if node['apache']['version'] == '2.4' -%>
# Include generic snippets of statements
IncludeOptional <%= node['apache']['dir'] %>/conf-enabled/*.conf

# Include the virtual host configurations:
IncludeOptional <%= node['apache']['dir'] %>/sites-enabled/*.conf
<% else -%>
# Include generic snippets of statements
Include <%= node['apache']['dir'] %>/conf-enabled/*.conf

# Include the virtual host configurations:
Include <%= node['apache']['dir'] %>/sites-enabled/*.conf
<% end -%>