Don't explode if flush() is called when an HTTP upload stream is closed.

Streams like BufferedOutputStream always call flush() even if it is
a no-op. These flushes must be permitted for compatibility with apps
that don't call close() until after the response has been retrieved.

Change-Id: Ic5c86ab6050c6c4d166c44ae5b4fc7a1688e7e45
http://b/3038470
4 files changed