* vendor: update cortex

Don't be blocked on https://github.com/cortexproject/cortex/pull/1345

 to
be merged and still maintain the fork

Signed-off-by: Goutham Veeramachaneni <gouthamve@gmail.com>

* add memcached ksonnet

Signed-off-by: Goutham Veeramachaneni <gouthamve@gmail.com>

* commit generated proto

Signed-off-by: Goutham Veeramachaneni <gouthamve@gmail.com>