Implement IPMI healthchecks

[craiganderson]

Add up-front checks and a report summary for IPMI accessibility and IPMI credentials validation of all supplied nodes in the environment (drydock.yaml).

[craiganderson]

Additionally, an up-front functional IPMI test (power off / power on) would be useful to address any IPMI issues (e.g., sometimes it's necessary to reset iLo/iDrac to make IPMI work again).

Separately, a version audit of OOB firmware versions would be useful to identify nodes which on different firmware versions, if not to audit against an expected version. (Some of the IPMI related issues were tired to nodes with bugged firmware versions).