prefetcher_test: Add more test conditions to make sure prefetch updates are moving up the prefetch tree correctly.
prefetcher_test: Add more test conditions to make sure prefetch updates are moving up the prefetch tree correctly.

keybase/kbfs,keybase/client,keybase/client,keybase/kbfs,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client