Fix integration tests after recent refactoring

[rhafer]

Force the use of the "noop" cache. The default "memory" is shared between the testcases and causes failures, after the metadata cache's key changed from paths.

[aduffeck]

lgm.

Just a remark though: posixfs requires a cache, so we'll have to figure out a way to have a clean cache for each test anyway. What we've done in other tests was setting the cache_database to something unique for each tests. Maybe something like

		conf["filemetadatacache"] = map[string]string{"cache_database": revads["storage"].StorageRoot}

could work.