fix: Write cursor into temporary file and move it

This deals with a potential issue where creating a new file in place
of an existing cursor position file may cause position files to be
empty.

The cause for this is that the newly created file will truncate the
previous content, if journaldriver is then terminated before it
completes the cursor write to this file, it will not have written a
valid cursor (or anything at all).

Potentially relates to #2

0 files changed, 0 insertions, 0 deletions