Backport of deployer: ensure the proxy/dns/pause containers do not continually get replaced due to a change in a docker default into release/1.17.x (#21044)

backport of commit a3950321a3

Co-authored-by: R.B. Boyer <rb@hashicorp.com>

testing/deployer/sprawl/internal/tfgen/templates/container-coredns.tf.tmpl

@@ -4,6 +4,7 @@ resource "docker_container" "{{.DockerNetworkName}}-coredns" {
   restart  = "always"
   dns      = ["8.8.8.8"]
 
+  network_mode = "bridge"
   networks_advanced {
     name         = docker_network.{{.DockerNetworkName}}.name
     ipv4_address = "{{.IPAddress}}"

testing/deployer/sprawl/internal/tfgen/templates/container-pause.tf.tmpl

@@ -23,6 +23,7 @@ ports {
 }
 {{- end }}
 
+network_mode = "bridge"
 {{- range .Node.Addresses }}
 networks_advanced {
   name         = docker_network.{{.DockerNetworkName}}.name

testing/deployer/sprawl/internal/tfgen/templates/container-proxy.tf.tmpl

@@ -8,6 +8,7 @@ resource "docker_container" "{{.DockerNetworkName}}-forwardproxy" {
     internal = {{.InternalPort}}
   }
 
+  network_mode = "bridge"
   networks_advanced {
     name         = docker_network.{{.DockerNetworkName}}.name
     ipv4_address = "{{.IPAddress}}"