test: fix permission issue if run as root

Always those silly mistakes. Do what I mean, not what I said…

Reported-By: Travis
Git-Dch: Ignore

test/integration/test-handle-redirect-as-used-mirror-change

@@ -38,5 +38,6 @@ Location: http://0.0.0.0:${APTHTTPPORT}/dists/unstable/main/source/Sources.gz
 Location: http://0.0.0.0:${APTHTTPPORT}/dists/unstable/main/binary-all/Packages.gz
 Location: http://0.0.0.0:${APTHTTPPORT}/dists/unstable/main/i18n/Translation-en.gz" grep '^Location:' aptarchive/webserver.log
 
+cd downloaded
 testsuccess apthelper download-file "http://localhost:${APTHTTPPORT}/redirectme/dists/unstable/InRelease" inrelease
 testsuccess test -s inrelease