The FilterFileSystem javadoc says "The class FilterFileSystem itself simply overrides all methods of FileSystem with versions that pass all requests to the contained file system." initialize(URI, Configuration) is part of the FileSystem API, and before
HADOOP-8013 it simply called fs.initialize(). After HADOOP-8013 it calls super.initialize() rather than delegating. This breaks a number of the Hive tests. Hive's ProxyLocalFileSystem would be able to work around this problem by calling setConf, but unfortunately FilterFileSystem does not override that method. We need to make FilterFileSystem call fs.initialize (instead of using super) and also override setConf.