Use with_list for Ansible < 2.5 compatibility

loop on Ansible < 2.5 throws an "Unexpected failure in finding the
lookup named" message. Fix that replacing loop with with_list.

Change-Id: Iecb0f67fcfadd017ef7c889d9cdada68da0d46e9

tasks/rpm_install.yml

@@ -30,7 +30,7 @@
   copy:
     src: "{{ item }}"
     dest: "{{ modify_dir_path }}"
-  loop: "{{ rpms_list }}"
+  with_list: "{{ rpms_list }}"
 
 - name: Write Dockerfile to {{ modify_dir_path }}
   template: