Remove unneeded setting of ansible_user

This never actually did anything because we are setting a variable
to itself. However, with ansible2.3 update this actually breaks.

Change-Id: I7ca4a29d0eeeacfe799d7640fcbecc9d88329be0

roles/ovb-manage-stack/tasks/ovb-create-stack.yml

@@ -102,7 +102,6 @@
       groups: "{{ node_groups| join(',') }}"
       ansible_host: "{{ undercloud_ip }}"
       ansible_fqdn: undercloud
-      ansible_user: "{{ ansible_user }}"
       ansible_private_key_file: "{{ undercloud_key }}"
       ansible_ssh_extra_args: "{{ ssh_extra_args }}"
       undercloud_ip: "{{ undercloud_ip }}"