largefiles: use separate try/except and try/finally as needed for python2.4

cfccd3bee7b3 introduced a try/except/finally block, which breaks compatibility
with python2.4

hgext/largefiles/overrides.py

@@ -320,6 +320,7 def override_copy(orig, ui, repo, pats,
     nonormalfiles = False
     nolfiles = False
     try:
+        try:
         installnormalfilesmatchfn(repo[None].manifest())
         result = orig(ui, repo, pats, opts, rename)
     except util.Abort, e:
@@ -339,6 +340,7 def override_copy(orig, ui, repo, pats,
         return result
 
     try:
+        try:
         # When we call orig below it creates the standins but we don't add them
         # to the dir state until later so lock during that time.
         wlock = repo.wlock()