CBQE-0 Add access_log param to observe

Change-Id: I29f8b11d92279d180f58e93b7db69a2d1f1d986f
Reviewed-on: http://review.couchbase.org/26588
Reviewed-by: Deepkaran Salooja <deepkaran.salooja@globallogic.com>
Tested-by: Deepkaran Salooja <deepkaran.salooja@globallogic.com>