Change throws clause for Hadoop23Shims.ProxyFileSystem23.access()

Looks like the changes from HIVE-7583 don't build correctly with Hadoop-2.6.0 because the ProxyFileSystem23 version of access() throws Exception, which is not one of the exceptions listed in the throws clause of FileSystem.access(). The method in ProxyFileSystem23 should have its throws clause modified to match FileSystem's.