MB-6939: increase XDCR checkpoint interval to 30 min
MB-6939: increase XDCR checkpoint interval to 30 min

XDCR will use priority checkpoint intead of regular checkpoints. To
address the overhead concern, we increase the checkpoint interval from
5 min to 30 min.

Change-Id: I128a2c826e3823084912bb6049a6390e2aec25d6
Reviewed-on: http://review.couchbase.org/21799
Reviewed-by: Damien Katz <99e6b749acbfbe2a596df99e91d24d6e1fdbee00@couchbase.com>
Tested-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

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