Simplify vars and callout in yum module

group_vars/all

 ---
 
-epel_release_url: http://ftp.ntua.gr/pub/linux/fedora-epel/6/i386/
-epel_release_name: epel-release-6-8.noarch.rpm
+epel_release: http://ftp.ntua.gr/pub/linux/fedora-epel/6/i386/epel-release-6-8.noarch.rpm
 
-arstats_release_url: http://rpm.hellasgrid.gr/mash/centos6-arstats/i386/
-arstats_release_name: ar-release-1.0.0-3.el6.noarch.rpm
+arstats_release: http://rpm.hellasgrid.gr/mash/centos6-arstats/i386/ar-release-1.0.0-3.el6.noarch.rpm

roles/repos/tasks/main.yml

 ---
 
 - name: Install epel repo files
-  yum: name={{ epel_release_url }}{{ epel_release_name }}
+  yum: name={{ epel_release }}
        state=present
   when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == '6'
 
 - name: Install arstats repo files
-  yum: name={{ arstats_release_url }}{{ arstats_release_name }}
+  yum: name={{ arstats_release }}
        state=present
   when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == '6'