sync: Fix force_checkout propagation

The force_checkout parameter was not propagated in all calls to
Checkout in Sync_LocalHalf.

Without this, repo sync --force-checkout can still fail for projects
currently on a local branch with no upstream/tracking configuration,
because the detach-to-manifest checkout was executed without -f,
leaving local modifications or untracked files able to block sync.

Change-Id: I58551388e2f906c4db96e220707a369057a71c24
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/579181
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josef Malmstrom <Josef.Malmstrom@arm.com>
Tested-by: Josef Malmstrom <Josef.Malmstrom@arm.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

project.py

@@ -1767,7 +1767,7 @@ class Project:
                 self, "leaving %s; does not track upstream", branch.name
             )
             try:
-                self._Checkout(revid, quiet=True)
+                self._Checkout(revid, force_checkout=force_checkout, quiet=True)
                 if submodules:
                     self._SyncSubmodules(quiet=True)
             except GitError as e: