Ubuntu.1804 Linux X64 benchmarks are hanging

[LoopedBard3]

This is a tracking issue for: dotnet/runtime#67545. We are seeing Perf_FileStream FlushAsync, ReadAsync, and WriteAsync causing hangs.

[adamsitnik]

@LoopedBard3 until the bug is fixed in runtime, we could use the following attribute to unblock the runs:

[OperatingSystemsFilter(allowed: true, OS.Windows)]

for

performance/src/benchmarks/micro/libraries/System.IO.FileSystem/Perf.FileStream.cs

Line 16 in e41db7c

public class Perf_FileStream

[LoopedBard3]

Perf_FileStream Reenabled per #2381.