MB-11458 Fix parsing of noop message from server

The upr server sends noop request and the upr client should
reply as response message. Currently the message parser expects
noop message from server to be response type. This assumption is
wrong.

Renamed no_op to noop to make it consistent in the upr client
implementation.

Change-Id: Id55ec6f483e340f2a51c1c8effe9e10e10479c3a
Reviewed-on: http://review.couchbase.org/38421
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>