Automatic merge from submit-queue
etcd3/watcher: Event.Object should have the same rev as etcd delete
### What's the problem?
When a delete is watched, the revision should be larger than any previous to guarantee ordering. However, currently etcd3 decodes the previous rev into returned object:
995f022808/pkg/storage/etcd3/watcher.go (L322)
This will break, for example, cacher's assumption here if it re-watch.
995f022808/pkg/storage/cacher.go (L579-L581)
The etcd2 impl. also takes the current ModifiedIndex to ensure it's a larger number:
995f022808/pkg/storage/etcd/etcd_watcher.go (L437-L442)
### What's this PR?
It fixes above problem by using etcd's delete revision.
d7cf4e60cb