Add protoproxy::localssl default_server and server_name parameters

default_server allows setting this server as the default server,
e.g. as fallback for SNI.
server_name allows a custom server name to be set, e.g. used
for SNI server selection.

Also enables default_server in role::cache::ssl

Change-Id: Ia2115f2540b261d56221c60fd9b245ee732a832b
Merge "Add protoproxy::localssl default_server and server_name parameters" into production