Fix "list comprehension redefines 'x'" warnings from pyflakes

  $ git ls-files | grep py$ | xargs pyflakes
  subcmds/stage.py:101: list comprehension redefines 'p' from line 63
  subcmds/sync.py:784: list comprehension redefines 'p' from line 664
  subcmds/upload.py:467: list comprehension redefines 'avail' from line 454

Change-Id: Ia65d1a72ed185ab3357e1a91ed4450c719e75a7c
diff --git a/subcmds/sync.py b/subcmds/sync.py
index d4432ce..8a043d9 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -780,8 +780,8 @@
       # generate a new args list to represent the opened projects.
       # TODO: make this more reliable -- if there's a project name/path overlap,
       # this may choose the wrong project.
-      args = [os.path.relpath(self.manifest.paths[p].worktree, os.getcwd())
-              for p in opened_projects]
+      args = [os.path.relpath(self.manifest.paths[path].worktree, os.getcwd())
+              for path in opened_projects]
       if not args:
         return
     all_projects = self.GetProjects(args,