[scenario] Factor out common nodes, states

[scenario] Factor out common nodes, states

Make the bulk of scenario files static again by shifting out all
common virtual nodes (mas01) and states (virtual_init, maas etc.)
to default.yaml(.j2).

This allows us to parse scenario-specific data during first j2
expansion, preparing for the new Pharos installer adapter that
relies on `conf.virtual.nodes.control` length to construct the
proper list of MaaS node definitions (kvm{01,02,03} vs {ctl01,gtw01}).

Change-Id: I666ab5bd6bb2a42f98646af51950f6b9fffa0e8b
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>