Fix the default logic in managing refs-filter The refs-filter logic was inherently broken, by considering an empty list of patterns as matching any string, potentially blocking processing of ref-updates. Align the logic between ExcludedRefsFilter and SyncRefsFilter giving the same common logic of how to manage defaults. Bug: Issue 15424 Change-Id: I7347555b30aafe94ae747440477f2a66ae71f34f