lint: clean up old statements

We can delete a number of disable statements that are no longer relevant,
replace the W/E/F constants with their human readable names, and scope a
few to where they're needed instead of disabling in the entire module.

BUG=None
TEST=`cros lint` is unchanged

Change-Id: Ic7ac1ab410917b075212b38412f8a1e381b8b915
Reviewed-on: https://chromium-review.googlesource.com/1135635
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
diff --git a/scripts/test_image_unittest.py b/scripts/test_image_unittest.py
index d03b93e..1859dfc 100644
--- a/scripts/test_image_unittest.py
+++ b/scripts/test_image_unittest.py
@@ -126,7 +126,7 @@
         self.tempdir
     ]
     test_image.main(argv)
-    # pylint: disable=W0212
+    # pylint: disable=protected-access
     self.assertEqual('my-board', test._board)
-    # pylint: disable=W0212
+    # pylint: disable=protected-access
     self.assertEqual('your-root', os.path.basename(test._result_dir))