Test code for observe in XDCR. Related to CBQE-932

Change-Id: Id739f6d7338845d771a57013dd91e1f7c4f6c203
Reviewed-on: http://review.couchbase.org/29384
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Shashank Gupta1 <shashank.gupta1@globallogic.com>