Fixed bug CLOUDSTACK-2216

The snapshots backups that have the field “removed” set are included in the validBackupUUIDs of CleanupSnapshotBackupCommand. This causes the bug, because any backup that has the removed field set should be deleted, thus, they should not be included in the validBackupUUIDs. This is fixed by adding a condition in the SQL query to exclude any backups that have removed field set.