Always use CHECKPOINT flag during TAP_CONNECT
Always use CHECKPOINT flag during TAP_CONNECT

This is accomplised by always passing empty list [] instead of
undefined for the vbucketId-to-checkpointId list.

Change-Id: I3b5c80a3db6f6ec1848bfa5b116b5e219196c195
Reviewed-on: http://review.couchbase.org/6798
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

membase/ns_server,ceejatec/ns_server,daverigby/ns_server,nimishzynga/ns_server,t3rm1n4l/ns_server,nimishzynga/ns_server,ceejatec/ns_server,mschoch/ns_server,nimishzynga/ns_server,pavel-blagodov/ns_server,daverigby/ns_server,membase/ns_server,vzasade/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,pavel-blagodov/ns_server,pavel-blagodov/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,pavel-blagodov/ns_server,mschoch/ns_server,membase/ns_server,ceejatec/ns_server,vzasade/ns_server,daverigby/ns_server,daverigby/ns_server,t3rm1n4l/ns_server,vzasade/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,t3rm1n4l/ns_server,mschoch/ns_server,membase/ns_server,daverigby/ns_server,vzasade/ns_server,membase/ns_server,ceejatec/ns_server,nimishzynga/ns_server