Use nginx module for protoproxy and disable notify

The protoproxy module was doing a lot of work the nginx module
should be doing instead. This change moves that work to the nginx
module. This change also disables notification of the service on
configuration changes so that we can properly depool hosts before
doing service restarts.

Change-Id: Ib364384b0400a59405d4722a175b73c0edffafa5
Merge "Use nginx module for protoproxy and disable notify" into production