tls_context: refactor common TLS context for downstream/upstream into shared message. (#118)
tls_context: refactor common TLS context for downstream/upstream into shared message. (#118)

Also add deprecated support for alt_alpn_protocols.
rshriram/envoy-api,jrajahalme/envoy-api,lyft/envoy-api,rshriram/envoy-api,jrajahalme/envoy-api,jrajahalme/envoy-api,lyft/envoy-api,jrajahalme/envoy-api,rshriram/envoy-api,lyft/envoy-api