Plugin was built extensively around podified/devstack setups, maybe more
types in the future.
It isn't likely to be changed any time soon, such change will require
adding code into plenty of conditions spread around plugin.
We can replace manually maintained configuration with automated check
to reduce CI maintenance upstream/downstream.
As documented for devstack [1] home directory can optionally be
`/opt/stack`, for this plugin's devstack jobs it is commonly used,
check should work to tell the difference.
[1] https://docs.openstack.org/devstack/latest/
Related-Bug: #OSPRH-16056
Related-Bug: #OSPRH-15819
Change-Id: I2d3f807b07e5eb810b87320e31cf64ad72f2f2a9
ea0e811aa9