Added debug switches to datapath.go

Change-Id: I8a2b62f8e226e8b0b676997136bd6c8a452ce490
Reviewed-on: http://review.couchbase.org/41173
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>