[CI] false possitive in upgrades job

[Jose Luis Franco]

The tripleo-ci-centos-7-scenario000-multinode-oooq-container-upgrades job is being displayed as PASSED in the CI results (https://review.openstack.org/#/c/582502/) , however when digging into the tasks executed, we can't see all multinode-overcloud-upgrade.yml playbook tasks being skipped.

http://logs.openstack.org/02/582502/7/check/tripleo-ci-centos-7-scenario000-multinode-oooq-container-upgrades/a3e357f/job-output.txt.gz#_2018-11-15_18_18_38_619727

When checking at the tags being used at the time of executing the different playbooks, we are missing the overcloud-upgrade one:

http://logs.openstack.org/02/582502/7/check/tripleo-ci-centos-7-scenario000-multinode-oooq-container-upgrades/a3e357f/job-output.txt.gz#_2018-11-15_15_32_31_546101

[Quique Llorente (quiquell)]

The issue is procuded by the following commit https://review.openstack.org/#/c/606948/, it removes mixed_upgrade flag, this is the flag used to differenciate overcloud upgrade.