Do not do quota enforcement if quota is "-"
Do not do quota enforcement if quota is "-"

(cherry picked from commit 710b1a09dda349422470b3c936b2f1e6c8b6ce9b)

uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend,uroni/urbackup_backend