Fix test build for CentOS 7.

tasks/main.yml

@@ -6,7 +6,7 @@
 
 # Include version-specific variables for RedHat.
 - name: Include OS-specific variables (RedHat).
-  include_vars: "{{ ansible_os_family }}-{{ ansible_distribution_version|slice(1) }}.yml"
+  include_vars: "{{ ansible_os_family }}-{{ ansible_lsb.major_release }}.yml"
   when: ansible_os_family == "RedHat"
 
 - name: Define mysql_packages.

tests/Dockerfile.centos-7

@@ -12,6 +12,8 @@ rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
 rm -f /lib/systemd/system/basic.target.wants/*; \
 rm -f /lib/systemd/system/anaconda.target.wants/*;
 
+RUN yum -y install redhat-lsb-core
+
 # Install Ansible
 RUN yum -y install epel-release
 RUN yum -y install git ansible sudo