'ansible_become' defined as a host_var or in the inventory for a host
has a higher precedence than 'become' defined within a playbook.
In change Id5b76a87809f03951c954fc3d752419a673403f7, 'become' was
defined explicitly for each play running against localhost so
'ansible_become' should be removed from its host_vars.
Change-Id: I27f46c3966877d5026c96345220d1f268deb971d
e56ad5b188