consul/connect: set default Envoy worker threads for gateways

[shoenig]

Applying the default --concurrency for gateways was missed before.
Set the default Envoy concurrency to 1 for connect gateways. The
same override value meta.connect.proxy_concurrency applies.

[shoenig]

spot check

gateway demo job

job "igfull" {
  
  datacenters = ["dc1"]

  group "example" {
    
    network {
      mode = "host"

      port "inbound" {
	static = 8080
      }

      port "envoy" {
	static = 19999
      }
    }

    service {
      name = "my-ingress-service"
      port = "envoy"

      connect {
	gateway {

	  // Consul gateway [envoy] proxy options.
	  proxy {
	    connect_timeout = "500ms"
	    envoy_gateway_bind_tagged_addresses = false
	  }

	  // Consul Ingress Gateway Configuration Entry
	  ingress {
	    tls {
	      enabled = false
	    }

	    // any number of listeners
	    listener {
	      port = 8080
	      protocol = "tcp"
	      // protocol = "http"
	      service {
		name = "uuid-api"
		// hosts = ["192.168.99.78"]
	      }
	    }
	  }
	}
      }
    }
  }

  group "generator" {
    network {
      mode = "bridge"
      port "api" {
	// nomads choice
	to = -1
      }
    }

    service {
      name = "uuid-api"
      port = "${NOMAD_PORT_api}"

      connect {
	native = true
      }
    }

    task "generate" {
      driver = "docker"

      config {
	image = "hashicorpnomad/uuid-api:v3"
      }

      env {
	BIND = "0.0.0.0"
	PORT = "${NOMAD_PORT_api}"
      }
    }
  }
}

using defaults

$ sudo nomad agent -dev

$ docker inspect 263 | jq .[].Args
[
  "-c",
  "/secrets/envoy_bootstrap.json",
  "-l",
  "info",
  "--concurrency",
  "1",
  "--disable-hot-restart"
]

using configured value

sudo nomad agent -dev -meta='connect.proxy_concurrency=3'

$ docker inspect 7b | jq .[].Args
[
  "-c",
  "/secrets/envoy_bootstrap.json",
  "-l",
  "info",
  "--concurrency",
  "3",
  "--disable-hot-restart"
]

[tgross]

LGTM

[github-actions]

I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions.
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