Do not install distro packages with a VENV activated

It can yield weird mixes of distro and venv python during installation.

Change-Id: I651b72efb3159609e8a4ebb54f48e390c21e9ca7

playbooks/roles/bifrost-ironic-install/tasks/install.yml

@@ -18,12 +18,10 @@
 
 - name: "Update Package Cache"
   apt: update_cache=yes
-  environment: "{{ venv }}"
   when: ansible_os_family == 'Debian'
 
 - name: "Install packages"
   action: "{{ ansible_pkg_mgr }} name={{ item }} state=present"
-  environment: "{{ venv }}"
   with_items: "{{ required_packages }}"
 
 - name: "If running in CI, set source install facts just to be sure"