buildman: Correct pylint errors

Fix pylint errors that can be fixed and mask those that seem to be
incorrect.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/builder.py b/tools/buildman/builder.py
index 754642d..ecbfa3e 100644
--- a/tools/buildman/builder.py
+++ b/tools/buildman/builder.py
@@ -1763,7 +1763,7 @@
             if self.num_threads:
                 self.queue.put(job)
             else:
-                results = self._single_builder.RunJob(job)
+                self._single_builder.RunJob(job)
 
         if self.num_threads:
             term = threading.Thread(target=self.queue.join)