[akraino] Add IEC K8-calico scenarios

[akraino] Add IEC K8-calico scenarios

- bump Pharos git submodule to allow PODs with fewer nodes;
- add `k8-calico-iec-noha` scenario definition for Akraino
  IEC basic configuration;
- add `k8-calico-iec-vcp-noha` scenario definition for Akraino
  IEC nested (virtualized control plane) configuration;
- add `akraino_iec` state, which will leverage the Akraino IEC
  bootstrap scripts from [1];
- replace system.reboot salt call with cmd.run 'reboot' as it's more
  reliable;
- use kernel 4.15 for AArch64 K8 IEC scenarios;

NOTE: These scenarios will not be released in OPNFV since don't rely
on Salt formulas but instead of Akraino IEC scripts to install K8s.

[1] https://gerrit.akraino.org/r/#/q/project:iec

Change-Id: I4e538e0563d724cd3fd5c4d462ddc22d0c739402
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>