FrameRequestStream/HttpRequestStream is not compatible with CryptoStream

[kekekeks]

System.NotSupportedException: Specified method is not supported.
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.FrameRequestStream.Flush()
   at System.Security.Cryptography.CryptoStream.FlushFinalBlock()
   at System.Security.Cryptography.CryptoStream.Dispose(Boolean disposing)

CryptoStream.Dispose is calling Flush on the underlying stream even if said stream is read only - https://github.com/dotnet/corefx/issues/27326

Apparently this is intended behavior of CryptoStream and Flush shouldn't ever throw exceptions: dotnet/corefx#27327 (review)

[davidfowl]

Fixed by #2342