sync: respect --force-sync when fetching manifest project updates

The --force-sync option was being passed down for all updates except
for the manifest project, so add that there too.

Bug: https://crbug.com/gerrit/11034
Change-Id: I33818b652f828c6b847dbc70f1fedfac5ac17bbe
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/228146
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

subcmds/sync.py

@@ -780,6 +780,7 @@ later is required to fix a server side protocol bug.
       start = time.time()
       success = mp.Sync_NetworkHalf(quiet=opt.quiet, verbose=opt.verbose,
                                     current_branch_only=opt.current_branch_only,
+                                    force_sync=opt.force_sync,
                                     tags=opt.tags,
                                     optimized_fetch=opt.optimized_fetch,
                                     retry_fetches=opt.retry_fetches,