largefiles: take lock before writing requirements

With `share-safe`, we will also write file in the store. We now take the `lock`
as needed.

Differential Revision: https://phab.mercurial-scm.org/D11992

hgext/largefiles/reposetup.py

@@ -455,6 +455,7 def reposetup(ui, repo):
     repo.prepushoutgoinghooks.add(b"largefiles", prepushoutgoinghook)
 
     def checkrequireslfiles(ui, repo, **kwargs):
+        with repo.lock():
         if b'largefiles' not in repo.requirements and any(
             lfutil.shortname + b'/' in f[1] for f in repo.store.datafiles()
         ):