Docs: Explaining dynamic inventory
Docs: Explaining dynamic inventory

Adding documentation to explain in more detail about the dynamic
inventory generation process.

Closes-Bug: 1554528

Change-Id: I399d703b680f8202407ae80d3b7dac05deb1dbfb

yanyao/openstack-ansible,Logan2211/openstack-ansible,bunchc/openstack-ansible,BjoernT/os-ansible-deployment,cloudnull/os-ansible-deployment,robb-romans/openstack-ansible,openstack/openstack-ansible,mrda/openstack-ansible,os-cloud/os-ansible-deployment,BjoernT/openstack-ansible,bunchc/openstack-ansible,openstack/openstack-ansible,BjoernT/os-ansible-deployment,BjoernT/openstack-ansible,stackforge/os-ansible-deployment,yanyao/openstack-ansible,major/os-ansible-deployment,mrda/openstack-ansible,cfarquhar/openstack-ansible,mrda/openstack-ansible,cloudnull/os-ansible-deployment,mancdaz/openstack-ansible,major/openstack-ansible,robb-romans/openstack-ansible,major/openstack-ansible,major/os-ansible-deployment,Logan2211/openstack-ansible,BjoernT/os-ansible-deployment,mancdaz/openstack-ansible,yanyao/newton,yanyao/newton,os-cloud/os-ansible-deployment,weezer/openstack-ansible,weezer/openstack-ansible,stackforge/os-ansible-deployment,cfarquhar/openstack-ansible