Fix parameter name for removing compute host
Fix parameter name for removing compute host

The compute parameter name is incorrect in the docs for removing
compute host from openstack. It should be 'host_to_be_removed'.

Change-Id: I0c35183215a6a776e13710ebdbc23fefe61f339b

openstack/openstack-ansible,stackforge/os-ansible-deployment,bunchc/openstack-ansible,stackforge/os-ansible-deployment,bunchc/openstack-ansible,openstack/openstack-ansible