Version 2.0.0 beta - Release Candidate 18

This commit includes many small fixes from testing of RC17;

Bug fixes of note;

• Fixed a bug(?) where, if a node was rebuilt and then later used to upload a file to the media library, it would fail because of the old SSH fingerprint not matching the new one. Now, we remove the offending key so that it starts working again on subsequent uploads. The is a questionable approach for security reasons and may be changed in a future release. For now, the logic is that the BCN is what dashboard -> node comms happen on and it is supposed to be secured and isolated.
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• Changed the default drbd c-plan-ahead to '1' and the default max-buffers to 8k on the advice of LINBIT staff to make DRBD 8.4 adjust the resync rate according to load better.
• Fixed a problem where trying to choose a CPU count for a server with a zero-pre-padded value stored as-is in the XML definition, which caused virsh to default to a single core.
• Fixed a bug in scan-storcli where a drive group wouldn't map to a controller UUID when the drive group vanished causing an error and exit.
• Fixed a bug in Get->server_host() where it would error out trying to check what servers were running on the peer whem the peer was offline.
• Fixed a bug in ScanCore where the '-v...' switches were not being honoured properly.
• Updated ScanCore's thermal "cool down" timers to count both thermal shutdowns and load sheds in the previous six hours.
• Fixed a bug where, if the peer was offline and the local node was in thermal warning, it would try to load shed.
• Upped the verbosity of logging in ScanCore's 'avoid_duplicate_run' function after a (so far unreproducable) bug where two copies of ScanCore managed to run at the same time.