Terminated event streams should conform chunked encoding format

[PetrGlad]

When Nakadi terminates event stream it just closes connection without sending closing empty chunk.
HTTP clients that strive to conform specifications raise errors as they try to read final chunk on stream that closes. This happens every time the stream is closed by Nakadi.

To conform chunked encoding format Nakadi should send final empty chunk when closing event stream.

References:

• https://en.wikipedia.org/wiki/Chunked_transfer_encoding
• https://tools.ietf.org/html/rfc7230#section-4.1

[lmontrieux]

Jira ticket ARUHA-832