neutrinonotify: persist rescan progress.
neutrinonotify: persist rescan progress.

Adding persistency to neutrino re-scan progress. In case the re-scan
failed in the middle or the node was restarted before the re-scan
has been completed this fix will start from the last point instead
of the beginning.
On long re-scan , such as old channels on mobile devices this is
crucial.

aakselrod/lnd,aakselrod/lnd