Tripleo-upgrades-fs-variables

Table with the variables from the tripleo-upgrades ansible role, they are used at the featureset. The containerize_overcloud_upgrade, overcloud_upgrade and mixed_upgrades are the same, we have to make them converge. The the _step variables are no longer used. The mixed_upgrade variable set the initial release of overcloud and undecloud

Fs variable	Undercloud	Overcloud
overcloud_upgrade: true and mixed_upgrade: true	n	n - 1 -> n
containerize_overcloud_upgrade: true and mixed_upgrade: true	n	n - 1 -> n
ffu_overcloud_upgrade and and mixed_upgrade: true	n + 3	n -> n + 3
ffu_undercloud_upgrade (not yet implemented)	n -> n + 3	noop
undercloud_upgrade	n -> n + 1	noop