Handle large output in v2 shim with TTY

Reized the I/O buffers to align with the size of the kernel buffers with fifos
and move the close aspect of the console to key off of the stdin closing.

Fixes #3738

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

pkg/process/io.go

@@ -40,7 +40,9 @@ import (
 
 var bufPool = sync.Pool{
 	New: func() interface{} {
-		buffer := make([]byte, 32<<10)
+		// setting to 4096 to align with PIPE_BUF
+		// http://man7.org/linux/man-pages/man7/pipe.7.html
+		buffer := make([]byte, 4096)
 		return &buffer
 	},
 }