Fix pylint warnings introduced by the submodule patch

"69998b0 Represent git-submodule as nested projects" has introduced a
few pylint warnings.

W0612:1439,8:Project._GetSubmodules.get_submodules: Unused variable 'sub_gitdir'
W0613:1424,36:Project._GetSubmodules.get_submodules: Unused argument 'path'
W0612:1450,25:Project._GetSubmodules.parse_gitmodules: Unused variable 'e'
W0622:516,8:Sync.Execute: Redefining built-in 'all'

Change-Id: I84378e2832ed1b5ab023e394d53b22dcea799ba4
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 28c154a..64ed38e 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -513,9 +513,9 @@
       previously_missing_set = set()
       while True:
         self.manifest._Unload()
-        all = self.GetProjects(args, missing_ok=True)
+        all_projects = self.GetProjects(args, missing_ok=True)
         missing = []
-        for project in all:
+        for project in all_projects:
           if project.gitdir not in fetched:
             missing.append(project)
         if not missing: