Update the swift base url to point directly at prodstack swift

Tim assures me the auth token in the name is read-only, and also exposed via
http redirects whenever one accesses the bucket via autopkgtest.u.c
frontend, so there is no security issue here; and accessing direct gets us
results even when the autopkgtest.db is out of date (which is the problem we
have right now that we want to route around).

britney.conf

@@ -100,7 +100,7 @@ ADT_PPAS          =
 ADT_SHARED_RESULTS_CACHE =
 # Swift base URL with the results (must be publicly readable and browsable)
 # or file location if results are pre-fetched
-ADT_SWIFT_URL     = https://autopkgtest.ubuntu.com/results/
+ADT_SWIFT_URL     = https://objectstorage.prodstack5.canonical.com/swift/v1/AUTH_0f9aae918d5b4744bf7b827671c86842/
 # Base URL for autopkgtest site, used for links in the excuses
 ADT_CI_URL        = https://autopkgtest.ubuntu.com/
 # URL for the autopkgtest database, if used