0.9.6-beta.7

Bugfix release for SMB locations, with occ backup:cancel to stop a backup that does not get
anywhere. Tested on a production instance: a first full backup of 151,021 files (807 GiB) to OVH
S3 completed, and a backup to a Hetzner Storage Box over SMB that had slowed to 12 GiB in 35
hours ran at about 5.6 MiB/s after the update, while the S3 backup was still reading.

Added

• The list of backup runs (web interface and occ backup:status) shows the total size of each
  backup next to what it uploaded: an incremental backup of 1 TB that uploads 800 MB now shows
  both. occ backup:status shows sizes in GiB where that reads better than MiB.
• occ backup:cancel <run> stops a running backup; occ backup:status shows the run numbers.
  No new step of the run starts, the step in progress finishes (usually within a minute), then
  the process working on the run (occ backup:run or cron) stops. What it already stored is
  removed by the next cleanup. A backup started by an earlier version is stopped as well: after
  two minutes it is marked cancelled while it works, and its process stops at the end of the
  step.

Fixed

• Backups to SMB locations, and to other slow locations with many packs, slowed to a crawl: each
  30-second step opened the location again, and reading the list of index files took longer
  than the step itself. Each step then stored a single 4 MiB pack, which made the list longer
  still. A first full backup of 0.8 TB to a Hetzner Storage Box over SMB managed 12 GiB in 35
  hours. occ backup:run and system cron now open the location once per run, opening no longer
  counts towards the step's time, and SMB folders are listed in one request instead of one per
  file. A backup to an SMB location that is not getting anywhere keeps running in its old
  process after the update: update first, then stop it with occ backup:cancel <run> and start
  it again. The new backup reuses the packs the old one stored.