FILES: Skip files that are not created yet
In order to avoid complex ordering logic, even if one file is updated,
we flush all the entries. In theory, we could only flush the individual
file and all the files preceding it, but it's safer to just create a
complete mirror every time.
And this can be problematic if one of the files we try to update is not
created yet during the update. This can happen e.g. when a file is not
created during early boot.
To solve this, try to be very defensive and always flush the whole
database, ignore ENOENT errors, but abort on all other errors.
Reviewed-by: Pavel Březina <pbrezina@redhat.com>