CBQE-0: Made checkpoint interval to 60 seconds default for each XDCR tests

Change-Id: Id5dbee13296fc523856838432c92ca0221b0ca61
Reviewed-on: http://review.couchbase.org/36522
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Aruna Piravi <aruna@couchbase.com>