Import backlog on new subscription.

Danger is when importing a new feed that may be maliciously crafted
to contain a zillion entries.

plugins/OStatus/scripts/testfeed.php

@@ -53,9 +53,11 @@ if (!$sub) {
     exit(1);
 }
 
+// XXX: This could maybe be replaced with $sub->importFeed()
+
 // Fetch the URL
 try {
-    $xml = HTTPClient::quickGet($feedurl, 'text/html,application/xhtml+xml');
+    $xml = HTTPClient::quickGet($feedurl, 'application/atom+xml');
 } catch (Exception $e) {
     echo sprintf("Could not fetch feedurl %s (%d).\n", $e->getMessage(), $e->getCode());
     exit(1);