zephyr_mirror: Don't display/log some useless "Skipping" notices.

In this case, if we're configured to not forward personals, there's no
point in logging a decision not to forward one.

(imported from commit 62c37591c6a70afb6235de626b0c6a3502cbcb27)

bots/zephyr_mirror_backend.py

@@ -257,6 +257,8 @@ def process_notice(notice, log):
         is_personal = True
 
     # Drop messages not to the listed subscriptions
+    if is_personal and not options.forward_personals:
+        return
     if (zephyr_class not in current_zephyr_subs) and not \
             (is_personal and options.forward_personals):
         logger.debug("Skipping ... %s/%s/%s" %