fix: rename pull_policies to pull_policy in config.toml (#1084)

## Description

The `runner_worker_docker_options` mentioned a `pull_policies` attribute
which was directly used in `config.toml` which is wrong. The correct
name is `pull_policy`. `pull_policy` is ignored by the Runner and has no
effect. Instead a pull policy of `always` is used automatically.

This PR renames the `pull_policies` to `pull_policy` before inserting it
into the configuration file. If `pull_policies` is used at the moment it
has no effect.

Closes #1065 

## Migrations required

In case `var.runner_worker_docker_options.pull_policy` is used, rename
`pull_policy` to `pull_policies` and make sure that it is a
`list(string)`, e.g. `pull_policies = ["always"]`

## Verification

Still to be done

- [X] `pull_policies` not given --> `pull_policy = ["always"] is used.
- [X] `pull_policies` given --> Specified value used

Author: kayman-mk

Diff for: locals.tf

@@ -54,9 +54,10 @@ locals {
 
   runners_docker_options_toml = templatefile("${path.module}/template/runners_docker_options.tftpl", {
     options = merge({
-      for key, value in var.runner_worker_docker_options : key => value if value != null && key != "volumes"
+      for key, value in var.runner_worker_docker_options : key => value if value != null && key != "volumes" && key != "pull_policies"
       }, {
-      volumes = local.runners_volumes
+      pull_policy = var.runner_worker_docker_options.pull_policies
+      volumes     = local.runners_volumes
     })
     }
   )
@@ -80,8 +81,6 @@ locals {
     }
   )
 
-  runners_pull_policies = "[\"${join("\",\"", var.runner_worker_docker_options.pull_policies)}\"]"
-
   /* determines if the docker machine executable adds the Name tag automatically (versions >= 0.16.2) */
   # make sure to skip pre-release stuff in the semver by ignoring everything after "-"
   docker_machine_version_used          = split(".", split("-", var.runner_install.docker_machine_version)[0])

Diff for: main.tf

@@ -113,7 +113,6 @@ locals {
       runners_executor                  = var.runner_worker.type
       runners_limit                     = var.runner_worker.max_jobs
       runners_concurrent                = var.runner_manager.maximum_concurrent_jobs
-      runners_pull_policies             = local.runners_pull_policies
       runners_idle_count                = var.runner_worker_docker_machine_instance.idle_count
       runners_idle_time                 = var.runner_worker_docker_machine_instance.idle_time
       runners_max_builds                = local.runners_max_builds_string

Diff for: tests/variables.tftest.hcl

@@ -8,8 +8,8 @@ run "create" {
   command = plan
 
   variables {
-    vpc_id = run.setup_tests.vpc_id
-    subnet_id = run.setup_tests.subnet_id
+    vpc_id      = run.setup_tests.vpc_id
+    subnet_id   = run.setup_tests.subnet_id
     environment = "test"
     runner_gitlab = {
       url = "https://my.fancy.url/not/used"
@@ -18,7 +18,7 @@ run "create" {
 
   # this is a dummy test. remove it as soon as the first real test is added
   assert {
-    condition = output.runner_role_name == "test-docker-machine"
+    condition     = output.runner_role_name == "test-docker-machine"
     error_message = "Plan failed"
   }
 }

Diff for: variables.tf

@@ -557,7 +557,7 @@ variable "runner_worker_docker_options" {
     disable_cache = "false"
     image         = "docker:18.03.1-ce"
     privileged    = "true"
-    pull_policy   = "always"
+    pull_policies = ["always"]
     shm_size      = 0
     tls_verify    = "false"
     volumes       = ["/cache"]