SSH drivers are being unsupported for about a year now. All current
stable branches of ironic are officially supporting IPMI-capable HW
simulation via virtualbmc.
All ironic-related gate jobs have already been switched
to not use or enable those drivers.
This patch finally removes SSH-based power and managemtnt driver interfaces
and all classic drivers using those from ironic code and documentation.
Related exceptions and `ssh_connect` function, together with dependency
on `paramiko` package are removed as well.
Change-Id: Ieda7249b9cd78e3be1eff37804996295fc8d3969
Closes-Bug: #1570301
Depends-On: I9b60c9fa24652e9e64e787cd4e5b0152f51e7a28
3d9895cc0b