Make sure we still support ERB templates when provided

`apache::mod::php` allowed to pass an ERB template, switching the
default template to EPP will break users that rely on this, so only
assume EPP template if the template name ends with .epp and process the
template as ERB in all other cases.

manifests/mod/php.pp

@@ -71,7 +71,10 @@
 
   $manage_content = $source ? {
     undef   => $content ? {
-      undef   => epp($template, { 'extensions' => $extensions }),
+      undef   => $template ? {
+        /\.epp\z/ => epp($template, { 'extensions' => $extensions }),
+        default   => template($template),
+      },
       default => $content,
     },
     default => undef,