improve skipping of non-zips based on feedback by Jesse

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1554838 13f79535-47bb-0310-9956-ffa450edef68
happy new year

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1554839 13f79535-47bb-0310-9956-ffa450edef68
don't set the use-caches flag for all connections, just for the one currently read from - caught by Jesse Glick

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1554840 13f79535-47bb-0310-9956-ffa450edef68