MB-11073: Force schedule snapshot only on deletion

Change-Id: I2e50c5da1684174b74e4b287b664db35ea780c28
Reviewed-on: http://review.couchbase.org/36867
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>