cli: update default redis and use nomad service discovery

Closes #12927
Closes #12958

This PR updates the version of redis used in our examples from 3.2 to 7.
The old version is very not supported anymore, and we should be setting
a good example by using a supported version.

The long-form example job is now fixed so that the service stanza uses
nomad as the service discovery provider, and so now the job runs without
a requirement of having Consul running and configured.

drivers/docker/config_test.go

@@ -21,10 +21,10 @@ func TestConfig_ParseHCL(t *testing.T) {
 		{
 			"basic image",
 			`config {
-				image = "redis:3.2"
+				image = "redis:7"
 			}`,
 			&TaskConfig{
-				Image:            "redis:3.2",
+				Image:            "redis:7",
 				Devices:          []DockerDevice{},
 				Mounts:           []DockerMount{},
 				MountsList:       []DockerMount{},
@@ -196,7 +196,7 @@ func TestConfig_ParseAllHCL(t *testing.T) {
 
 	cfgStr := `
 config {
-  image = "redis:3.2"
+  image = "redis:7"
   image_pull_timeout = "15m"
   advertise_ipv6_address = true
   args = ["command_arg1", "command_arg2"]
@@ -342,7 +342,7 @@ config {
 }`
 
 	expected := &TaskConfig{
-		Image:             "redis:3.2",
+		Image:             "redis:7",
 		ImagePullTimeout:  "15m",
 		AdvertiseIPv6Addr: true,
 		Args:              []string{"command_arg1", "command_arg2"},

drivers/docker/driver_test.go

@@ -2292,7 +2292,7 @@ func TestDockerDriver_AuthConfiguration(t *testing.T) {
 			AuthConfig: nil,
 		},
 		{
-			Repo: "redis:3.2",
+			Repo: "redis:7",
 			AuthConfig: &docker.AuthConfiguration{
 				Username:      "test",
 				Password:      "1234",
@@ -2301,7 +2301,7 @@ func TestDockerDriver_AuthConfiguration(t *testing.T) {
 			},
 		},
 		{
-			Repo: "quay.io/redis:3.2",
+			Repo: "quay.io/redis:7",
 			AuthConfig: &docker.AuthConfiguration{
 				Username:      "test",
 				Password:      "5678",
@@ -2310,7 +2310,7 @@ func TestDockerDriver_AuthConfiguration(t *testing.T) {
 			},
 		},
 		{
-			Repo: "other.io/redis:3.2",
+			Repo: "other.io/redis:7",
 			AuthConfig: &docker.AuthConfiguration{
 				Username:      "test",
 				Password:      "abcd",

drivers/docker/test-resources/docker/reconciler_containers_list.json

@@ -4,7 +4,7 @@
     "Names": [
       "/redis-72bfa388-024e-a903-45b8-2bc28b74ed69"
     ],
-    "Image": "redis:3.2",
+    "Image": "redis:7",
     "ImageID": "sha256:87856cc39862cec77541d68382e4867d7ccb29a85a17221446c857ddaebca916",
     "Command": "docker-entrypoint.sh redis-server",
     "Created": 1568383081,