hg: acquire wlock while updating the working directory via updatetotally

updatetotally() might be invoked outside wlock scope (e.g. invocation
via postincoming() at "hg unbundle" or "hg pull").

In such case, acquisition of wlock is needed for consistent view,
because parallel "hg update" and/or "hg bookmarks" might change
working directory status while executing updatetotally().

Strictly speaking, truly consistent updating should acquire also store
lock, because active bookmark might be moved to another one outside
wlock scope (e.g. pulling from other repository causes updating
current active one).

Acquisition of wlock in this patch ensures consistency in as same
level as past "hg update".

mercurial/hg.py

@@ -714,7 +714,7 b' def updatetotally(ui, repo, checkout, br'
 
     This returns whether conflict is detected at updating or not.
     """
-    if True:
+    with repo.wlock():
         movemarkfrom = None
         warndest = False
         if checkout is None: