[virtual] Split 'pxebr' from 'mcpcontrol' net

[virtual] Split 'pxebr' from 'mcpcontrol' net

- add new virsh managed network 'pxebr' (to mimic baremetal behavior
  on virtual PODs, this will be the equivalent of PXE/admin network);
- connect 'pxebr' to 3rd interface for cfg01, mas01 for all deploys
  (used to be baremetal-specific), replacing 'internal';
- keep 'mcpcontrol' connected only to 'cfg01' (+ 'mas01' if present)
  for initial infrastructure bring-up (1st interface);
- switch all virtual cluster nodes to 'pxebr' (1st interface);
- use 'pxebr' for all Salt cluster nodes traffic, 'mcpcontrol' only
  for mas01<=>cfg01 Salt traffic;
- convert <user-data.template> to jinja2 and expand it based on PDF
  instead of using `envsubst`;
- split <user-data.sh.j2> into two versions, one for each network
  used for Salt traffic;
- ci/deploy.sh: Read scenario data before template parsing for
  cluster domain variable, needed in virsh network def;
- leave docs diagram refresh to later after all possible deploy types
  have settled;
- limit keyserver proxy usage to nodes where the configured http proxy
  matches the first nameserver (true for all MaaS-provisioned nodes),
  so we can re-use the same pillar for FN VMs and baremetal nodes;
- add PXE/admin IP on cfg01's 3rd interface and switch other vnodes
  `salt_master_host` to point to it;

JIRA: FUEL-322

Change-Id: Ie4f7aedddf2ef81046f1127b377d88dce79f0fda
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>