Add fedora coreos driver. To deploy clusters with fedora coreos operators
or users need to add os_distro=fedora-coreos to the image. The scripts
to deploy kubernetes on top are the same with fedora atomic. Note that
this driver has selinux enabled.

The startup of the heat-container-agent uses a workaround to copy the
SoftwareDeployment credentials to /var/lib/cloud/data/cfn-init-data.
The fedora coreos driver requires heat train to support ignition.

Task: 29968
Story: 2005201

Signed-off-by: Spyros Trigazis <spyridon.trigazis@cern.ch>

(cherry picked from commit 73dc57c3)
Change-Id: Iffcaa68d385b1b829b577ebce2df465073dfb5a1