Fix bustage for bug 616185: commas are encoded as %2C in Bugzilla 3.x, but not in 2.22

Bugzilla/Install/DB.pm

@@ -3492,6 +3492,8 @@ sub _migrate_user_tags {
            undef, ($user_id, $tag_name));
 
         $query =~ s/^bug_id=//;
+        # Commas in Bugzilla 3.x are encoded as %2C, but not in 2.22.
+        $query =~ s/%2C/,/g
         my @bug_ids = split(/[\s,]+/, $query);
         $sth_bug_tag->execute($_, $tag_id) foreach @bug_ids;