added os-update playbook for debian

roles/os-updates/tasks/update_mirrors.yaml

@@ -0,0 +1,16 @@
+- name: Backup existing sources.list
+  copy:
+    src: /etc/apt/sources.list
+    dest: /etc/apt/sources.list.bak
+    remote_src: yes
+    force: yes
+
+
+- name: Update sources.list with new mirrors
+  template:
+    src: sources.list.j2
+    dest: /etc/apt/sources.list
+
+- name: Update apt cache
+  apt:
+    update_cache: yes