Fix onboarding link
Fix onboarding link

The onboarding link was not explicit and caused an anchor issue
with doc8 [1].

This should fix it.

[1]: http://logs.openstack.org/78/558878/2/check/openstack-ansible-linters/3bcf40f/job-output.txt.gz#_2018-04-05_04_08_37_863690

Change-Id: I5e0282f2899f26c220193ab77760684cebd22f39

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