Replace `WB_CONF.openstack_type` with code obtaining information.

Currently `WB_CONF.openstack_type` options are either devstack/podified, possibly more in the future.
Both setups have distinct easily checked conditions to differ them, currently checking one is sufficient since 2 options exist.

For example - devstack as documented [1] runs tempest tests as `stack` user which has `sudo` privileges and can check `/opt/stack` home directory existence (that is commonly used to store all deployed devstack setups).

Notice:
Changes will be needed on RDO upstream whitebox job, upstream whitebox devstack jobs, downstream component/integration jobs - but last time for this configuration

More details in parent story.

[1] https://docs.openstack.org/devstack/latest/