lint: fix a few redefined-argument-from-local warnings

Newer pylint catches a few cases where we shadow variables in the
current scope.  This is usually unintentional, so just rework the
code to avoid it.  It's innocuous in some of our files, but in
others (like upload_symbols) it's downright confusing.

BUG=chromium:980619
TEST=unittests pass
TEST=`CrOS lint` is unchanged

Change-Id: If8e66c84359ea51421e9ae5196583938948f333e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1812027
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/cli/deploy.py b/cli/deploy.py
index 13be3c8..f37a722 100644
--- a/cli/deploy.py
+++ b/cli/deploy.py
@@ -720,10 +720,10 @@
 
     num_updates = 0
     listed_installs = []
-    for cpv, _, listed, update in installs.values():
+    for cpv, _, listed, isupdate in installs.values():
       if listed:
         listed_installs.append(cpv)
-      if update:
+      if isupdate:
         num_updates += 1
 
     logging.info('Processed %d package(s), %d will be installed, %d are '