MB-100: XDCRUpgradetests

- Wait for replication to catch up
- Introduce sufficient time for upgrade+replication
- setting XDCR_FAILURE_RETRY_INTERVAL to 1 (Internal Settings)

Change-Id: I897340c1b7de205024846431be32879c93479cd2
Reviewed-on: http://review.couchbase.org/28420
Reviewed-by: abhinav dangeti <abhinav.dangeti@gmail.com>
Tested-by: abhinav dangeti <abhinav.dangeti@gmail.com>