Over the months the original meaning of ALLOW_OFFLINE and ALLOW_ONLINE have be
lost, and there is now a confusing mixture of uses in the source tree. With this
commit we make it clear the UPDATABLE flag is used to specify when the device is
updatable (e.g. from the desktop live session, or from the systemd offline
updates mode, or both) and the NEEDS_REBOOT flag lets us know when the update
is actually going to be done.
For instance, a UEFI UpdateCapsule can be *scheduled* from either the desktop
or from the update mode (but the latter would be a bit weird), but does require
a reboot. Some devices might only be updatable outside the live session, for
instance a hard drive update or a GPU update -- there's just too much going on
with a live session and we want to tightly control what's running during the
firmware flash.
This also means we don't have to "retry" the update when scheduling an update
that really can be scheduled whenever, but just requires a reboot to apply.
Although we supported other hashes than SHA1 (which is now moderately unsafe)
we had to switch the metadata provider and daemon on some kind of flag day to
using SHA256. Since that's somewhat impractical, just allow multiple checksums
to be set on objects and just try to match whatever is given in preference
order.
This also means we can easily transition to other hash types in the future.
The removed API was never present in a tarball release, so not an API break.
