Test that DeflateStream.Read does read an empty stream. Covers #19313.
Removed DeflateStream.UnmanagedRead Read loop. Fixes #19313.
If the base_stream was a NetworkStream UnmanagedRead loop would call base_stream.Read a second time and block until one byte was available to return. Without the loop UnmanagedRead will only read the base_stream once.
Merge pull request #1066 from esdrubal/bug19313

Changed DeflateStream to stop reading base_stream sooner. Fixes #19313.