Windows: failing unit tests in libstd\rt\uv\file.rs

[vadimcn]

file_test_full_simple
failed in non-task context at 'assertion failed: uverr.is_none()', C:\Rust\src\libstd\rt\uv\file.rs:312
file_test_full_simple_sync
failed in non-task context at 'assertion failed: result.is_ok()', C:\Rust\src\libstd\rt\uv\file.rs:374