upr client: fix missing snapshot_marker in the stream events

The order of components in the snapshot_marker message was parsed
in the wrong order and hence snapshot_markers were not appearing
through get_stream_event() calls.

Change-Id: Ie401ab43c99c27f3963ee76cab761aed2f86985a
Reviewed-on: http://review.couchbase.org/34182
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>