Merge branch 'refs/heads/t/sideband-cleanup'

started on 2016-07-03, cooking since 2016-07-16

para_server announces sideband as an optional feature, which is
pointless since sideband connections have become mandatory in
paraslash-0.5.x, so they are always used. This patch set removes
the feature negitiation during the initial handshake. The sideband
protocol remains and is not affected.

Overwiew of the handshake in v0.5.x:
	(SA) server announces sideband
	(CC) client fails connection if server did not announce sideband
	(CR) client requests sideband
	(SC) server fails connection if sideband was not requested
	already broken
		- client-0.4/server-0.5 (!CR, SC)
		- client-0.5/server-0.4 (!SA, CC)

Conversion plan:
	rm (CC): breaks nothing
	rm (SC): breaks nothing
	rm (CR): breaks cl-0.6/server-0.5 (!CR, SC)
	rm (SA): breaks cl-0.5/server-0.6 (!SA, CC)
	server fails connection if client requests sideband

In this series only the first two conversion steps are done as they
can be merged early without breaking anything.

* refs/heads/t/sideband-cleanup:
  server: Do not fail if client does not request sideband.
  client: No longer fail connection if sideband was not announced.