consul/connect: set default Envoy worker threads for gateways

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.

nomad/job_endpoint_hook_connect.go

@@ -46,6 +46,7 @@ var (
 			"args": []interface{}{
 				"-c", structs.EnvoyBootstrapPath,
 				"-l", "${meta.connect.log_level}",
+				"--concurrency", "${meta.connect.proxy_concurrency}",
 				"--disable-hot-restart",
 			},
 		}

website/pages/docs/upgrade/upgrade-specific.mdx

@@ -14,6 +14,16 @@ upgrade. However, specific versions of Nomad may have more details provided for
 their upgrades as a result of new features or changed behavior. This page is
 used to document those details separately from the standard upgrade flow.
 
+## Nomad 1.0.1
+
+#### Envoy worker threads
+
+Nomad v1.0.0 changed the default behavior around the number of worker threads
+created by the Envoy when being used as a sidecar for Consul Connect. In Nomad
+v1.0.1, the same default setting of [`--concurrency=1`][envoy_concurrency] is set for Envoy when used
+as a Connect gateway. As before, the [`meta.connect.proxy_concurrency`][proxy_concurrency]
+property can be set in client configuration to override the default value.
+
 ## Nomad 1.0.0
 
 ### HCL2 for Job specification