xdcr babysitting

Change-Id: I96af84b15e257b71b4633caa4aba716f0f69831f
Reviewed-on: http://review.couchbase.org/43372
Reviewed-by: Xiaomei Zhang <xiaomeizhangatwork@gmail.com>
Tested-by: Xiaomei Zhang <xiaomeizhangatwork@gmail.com>