Add yamllint to linters check

Change-Id: Iab88f866bc5253df09ea574576256e7fb0c11414

.yamllint.yml

@@ -0,0 +1,13 @@
+---
+extends: default
+ignore: |
+  .tox/
+rules:
+  line-length:
+    max: 120
+    level: warning
+  braces:
+    min-spaces-inside: 1
+    max-spaces-inside: 1
+    min-spaces-inside-empty: 0
+    max-spaces-inside-empty: 0

tox.ini

@@ -39,3 +39,4 @@ commands =
     bash -c 'printf -- "- name: frrouting\n  src: git+file://{toxinidir}\n" > {envdir}/test-requirements.yml'
     ansible-galaxy install -r {envdir}/test-requirements.yml --roles-path {envdir} --force
     ansible-lint {toxinidir}/tests/test.yml
+    yamllint {toxinidir}