largefiles: ensure that the standin files are available in getlfilestoupload()

The function only adds the hash content of the file to the set to upload if the
file in the ctx is a standin.  It is called by overrides.summaryremotehook(),
which is called in the summary method.  The largefiles extension switches
'lfstatus' on in summary, so the standins shouldn't be visible when obtaining a
context there.

The reason this wasn't noticed before is that the 'lfstatus' attribute is only
being set on the unfiltered repo because of how repoview delegates attribute
assignment.  Therefore any filtered view will return a context containing
standins, whether or not 'lfstatus' was set in the various overrides methods.
That will be fixed in the next patch.  But without this change, the next patch
would have test failures for 'summary --large' stating there are no files to
upload.

hgext/largefiles/lfutil.py

@@ -422,7 +422,14 b' def getlfilestoupdate(oldstandins, newst'
 def getlfilestoupload(repo, missing, addfunc):
     for n in missing:
         parents = [p for p in repo.changelog.parents(n) if p != node.nullid]
-        ctx = repo[n]
+
+        oldlfstatus = repo.lfstatus
+        repo.lfstatus = False
+        try:
+            ctx = repo[n]
+        finally:
+            repo.lfstatus = oldlfstatus
+
         files = set(ctx.files())
         if len(parents) == 2:
             mc = ctx.manifest()