This patch is sufficient to resolve regressions on Windows before we merge
HDFS-4949 to trunk. Summary:
- Stub native implementations of mlock_native and munlock_native, just enough for a successful compile and link of hadoop.dll.
- TestFsDatasetCache must skip tests if running on Windows or native code is not loaded.
- Fixed failure to shutdown a MiniDFSCluster in TestPathBasedCacheRequests, which would cause file handle leaks and failures on Windows due to file locking.
Andrew Wang and Colin P. McCabe, would you please review? Thanks!