Remove redundant python-apt install

Ansible automatically installs the python-apt package when using
the 'apt' Ansible module, if python-apt is not present. This patch
removes the (unneeded) explicit installation in the Kubespray
'preinstall' role.

roles/kubernetes/preinstall/tasks/main.yml

@@ -147,10 +147,8 @@
   tags: bootstrap-os
 
 
-- name: Install latest version of python-apt for Debian distribs
+- name: Update package management cache (APT)
   apt:
-    name: python-apt
-    state: latest
     update_cache: yes
     cache_valid_time: 3600
   when: ansible_os_family == "Debian"