Enable Robot Tests

Enabling robot tests in CI/CD pipeline
Propagate the parameter DO_ROBOT to stage_3-merge
Setting OSM_HOSTNAME for robot test execution
Adding prometheus_hostname env variable for ci/cd tests
Archive containers logs in robot test execution

Change-Id: I2d65050dd0e3cd7eb683120dd5696914bb91abff
Signed-off-by: beierlm <mark.beierl@canonical.com>
Author: Felipe Vicens <felipe.vicens@atos.net>