op-mode: T6133: add support to manually trigger commit-archive update

Automatic update of the remote commit-archive could fail under certian
circumstances, add an op-mode command to manually trigger the update:

cpo@LR1.wue3# run force commit-archive
Archiving config...

git+https://git.FOOO.de/cpo/vyos-config-backup [edit]

(cherry picked from commit 09de453194e9f8e7aa5dcb2e5c8de5a89e82708d)