make-centos-flight: Create a flight with CentOS as dom0

make-centos-flight: Create a flight with CentOS as dom0

This is based on make-flight, with the added all_host_os=centos runvar,
and without test that can not be run.

Anything based on the recipe "test-debian" or "test-pair" is remove, as
they require xen-tools. There is no XSM tests as the CentOS packages is
built without. There is no build jobs as the Xen packages been tested
are built in the CentOS CBS.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>