Adding yamllinter to ci steps (#1556)

* Adding yaml linter to ci check

* Minor linting fixes from yamllint

* Changing CI to install python pkgs from requirements.txt

- adding in a secondary requirements.txt for tests
- moving yamllint to tests requirements

roles/docker/vars/debian.yml

@@ -1,3 +1,4 @@
+---
 docker_kernel_min_version: '3.10'
 
 # https://apt.dockerproject.org/repo/dists/debian-wheezy/main/filelist

roles/docker/vars/fedora-20.yml

@@ -1,3 +1,4 @@
+---
 docker_kernel_min_version: '0'
 
 # versioning: docker-io itself is pinned at docker 1.5

roles/docker/vars/fedora.yml

@@ -1,3 +1,4 @@
+---
 docker_kernel_min_version: '0'
 
 # https://docs.docker.com/engine/installation/linux/fedora/#install-from-a-package

roles/docker/vars/redhat.yml

@@ -1,3 +1,4 @@
+---
 docker_kernel_min_version: '0'
 
 # https://yum.dockerproject.org/repo/main/centos/7/Packages/
@@ -8,7 +9,7 @@ docker_versioned_pkg:
   '1.12': docker-engine-1.12.6-1.el7.centos
   '1.13': docker-engine-1.13.1-1.el7.centos
   'stable': docker-engine-17.03.0.ce-1.el7.centos
-  'edge':  docker-engine-17.03.0.ce-1.el7.centos
+  'edge': docker-engine-17.03.0.ce-1.el7.centos
 
 # https://docs.docker.com/engine/installation/linux/centos/#install-from-a-package
 # https://download.docker.com/linux/centos/7/x86_64/stable/Packages/