Use min-free-space-size as a replacement for min-free-space-percent.
Previously, flatpak used to disable min-free-space-percent by re-writing
the config with min-free-space-percent=0. As the new version of ostree (2018.7)
now supports min-free-space-size, we should use that and migrate from -percent
option in existing repos to -size=500MB.
Config is rewritten with min-free-space-size in case of:
1) It has min-free-space-percent=0 only. (That is probably from the
previous re-writes).
2) If there are no min-free-space-* options.
Other than that, the config remains unchanged and the co-existence(if any)
of these options is governed by ostree.
https://github.com/flatpak/flatpak/issues/1826Closes: #1912
Approved by: alexlarsson
13610e3ed3