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

[vadimcn]

file_test_io_smoke_test
file_test_io_non_positional_read
file_test_io_seek_and_tell_smoke_test
file_test_io_seek_and_write
file_test_io_seek_shakedown

These all output task <unnamed> failed at 'Unhandled condition: io_error: {kind: OtherIoError, desc: "unknown error", detail: None}', C:\Rust\src\libstd\condition.rs:43 and crash test runner process.