In servo_server.servod.hwinit(), log full exception tracebacks.

Previously only the exception itself was logged when a control
initialization failed.  This should help with troubleshooting such
failures.

BRANCH=none
BUG=b:117848487
TEST=Ran servod in an environment that triggered multiple control
initialization errors.  Full tracebacks were logged.

Change-Id: Ic721721422f4d01df45d5999f1c3f5fd5c512f77
Signed-off-by: Matthew Blecker <matthewb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1286216
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>
diff --git a/servo/servo_server.py b/servo/servo_server.py
index f5eb283..79c77d2 100755
--- a/servo/servo_server.py
+++ b/servo/servo_server.py
@@ -834,9 +834,9 @@
           self.set(control_name, value)
         if verbose:
           self._logger.info('Initialized %s to %s', control_name, value)
-      except Exception as e:
-        self._logger.error('Problem initializing %s -> %s :: %s', control_name,
-                           value, str(e))
+      except Exception:
+        self._logger.exception(
+            'Problem initializing %s -> %s', control_name, value)
 
     # Init keyboard after all the intefaces are up.
     self._keyboard = self._init_keyboard_handler(self, self._board)