Allow manual hosts entry exports in overcloud.

This makes it possible to have SSL connections to APIs from compute
hosts with no DNS or external connectivity - something the
ci-overcloud has.

Change-Id: I089ef8fdfb4a59279f09bf3cd2a4474000e4bfa6
Support TripleO-CI for overcloud builds.

For Tripleo-CI we can't generate the key in the VM and hand it out,
because we have restricted access to the machine. Plus, this has been
ugly forever. Pass an SSH key in, rather than pulling one out.

Change-Id: I1def0757758e30e63891ff099106dac158bd8d83
Merge "Allow manual hosts entry exports in overcloud."
Merge "Support TripleO-CI for overcloud builds."