Add CleanupRemoteStorages command

cleanup files, address review

Fix CleanupRemoteStoragesTest tests

Fix test expectation.
Added files count to check filecache deletion.

Sort by numeric id for deterministic test results

Removed precise order test and added storage check

Remove inaccurate removal message check which has a different order on
Oracle.

Added more checks to confirm that existing storages still exist.

Signed-off-by: Morris Jobke <hey@morrisjobke.de>