Fix swift functional test

The swift functional test "test_delayed_delete_with_auth" was failing
with a permission error trying to write to /var/lib/glance.

Change the test's scrubber_datadir to be /tmp which is world writable.

Fixes bug 1291512.

Change-Id: I522c95619db26d009bd2ecb12fd02cb2eca56569
Merge "Fix swift functional test"