Use a separate runner for light CI jobs (#5771)

.gitlab-ci/lint.yml

@@ -2,6 +2,7 @@
 yamllint:
   extends: .job
   stage: unit-tests
+  tags: [light]
   variables:
     LANG: C.UTF-8
   script:
@@ -11,6 +12,7 @@ yamllint:
 vagrant-validate:
   extends: .job
   stage: unit-tests
+  tags: [light]
   variables:
     VAGRANT_VERSION: 2.2.4
   script:
@@ -20,6 +22,7 @@ vagrant-validate:
 ansible-lint:
   extends: .job
   stage: unit-tests
+  tags: [light]
   # lint every yml/yaml file that looks like it contains Ansible plays
   script: |-
     grep -Rl '^- hosts: \|^  hosts: ' --include \*.yml --include \*.yaml . | xargs -P 4 -n 25 ansible-lint -v
@@ -28,6 +31,7 @@ ansible-lint:
 syntax-check:
   extends: .job
   stage: unit-tests
+  tags: [light]
   variables:
     ANSIBLE_INVENTORY: inventory/local-tests.cfg
     ANSIBLE_REMOTE_USER: root
@@ -43,6 +47,7 @@ syntax-check:
 
 tox-inventory-builder:
   stage: unit-tests
+  tags: [light]
   extends: .job
   before_script:
     - ./tests/scripts/rebase.sh
@@ -56,6 +61,7 @@ tox-inventory-builder:
 
 markdownlint:
   stage: unit-tests
+  tags: [light]
   image: node
   before_script:
     - npm install -g markdownlint-cli