[OSAD doc] Update link to Cloud Admin Guide
[OSAD doc] Update link to Cloud Admin Guide

Update link to the Cloud Admin Guide after the RST conversion
of that book altered URLs.

Change-Id: Iaae1ad5843b5c36ce2abb965f88409e23719633b

mrda/openstack-ansible,BjoernT/openstack-ansible,mrda/openstack-ansible,achekunov/openstack-ansible,yanyao/openstack-deployment-liberty,cfarquhar/openstack-ansible,Logan2211/openstack-ansible,git-harry/os-ansible-deployment,major/openstack-ansible,antonym/openstack-ansible,manuelfelipe/openstack-ansible,yanyao/openstack-ansible,Logan2211/openstack-ansible,antonym/openstack-ansible,shane-c/openstack-ansible,shane-c/openstack-ansible,jpmontez/os-ansible-deployment,weezer/openstack-ansible,jpmontez/openstack-ansible,yanyao/newton,AlphaStaxLLC/os-ansible-deployment,openstack/openstack-ansible,yanyao/openstack-deployment-liberty,sti-jans/openstack-ansible,robb-romans/openstack-ansible,shane-c/openstack-ansible,os-cloud/os-ansible-deployment,manuelfelipe/openstack-ansible,antonym/openstack-ansible,git-harry/os-ansible-deployment,sti-jans/openstack-ansible,cfarquhar/openstack-ansible,bunchc/openstack-ansible,mancdaz/openstack-ansible,bunchc/openstack-ansible,AlphaStaxLLC/os-ansible-deployment,mancdaz/openstack-ansible,jpmontez/openstack-ansible,jpmontez/os-ansible-deployment,mrda/openstack-ansible,jpmontez/openstack-ansible,yanyao/openstack-ansible,robb-romans/openstack-ansible,stackforge/os-ansible-deployment,open-switch/infra_openstack-ansible,BjoernT/os-ansible-deployment,jpmontez/os-ansible-deployment,open-switch/infra_openstack-ansible,major/os-ansible-deployment,yanyao/newton,BjoernT/os-ansible-deployment,sti-jans/openstack-ansible,open-switch/infra_openstack-ansible,manuelfelipe/openstack-ansible,cloudnull/os-ansible-deployment,git-harry/os-ansible-deployment,achekunov/openstack-ansible,BjoernT/os-ansible-deployment,weezer/openstack-ansible,openstack/openstack-ansible,achekunov/openstack-ansible,BjoernT/openstack-ansible,os-cloud/os-ansible-deployment,major/os-ansible-deployment,AlphaStaxLLC/os-ansible-deployment,stackforge/os-ansible-deployment,major/openstack-ansible,yanyao/openstack-deployment-liberty,cloudnull/os-ansible-deployment