Do not try to increase cache size for upgrade if current db version is smaller than 15
Do not try to increase cache size for upgrade if current db version is smaller than 15

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