Add temperature raw value in syslog, only log if normalized "health" value is below 100%

[thomas303]

Forwarding from ​https://bugs.launchpad.net/ubuntu/+source/smartmontools/+bug/1653560

syslog entries like

Jan 2 20:22:27 server smartd[876]: Device: /dev/sda [SAT], SMART Usage Attribute: 194 Temperature_Celsius changed from 110 to 112

should be less confusing and logging should by default only take place if something is worth to be warned about.

That said, a "health" value below 100% (e.g. 98%) should trigger the logging, because then the health status as specified by the vendor is no more perfect.

And the output could be more verbose and less confusing. I suggest:

Jan 2 20:22:27 server smartd[876]: Device: /dev/sda [SAT], SMART Usage Attribute: 194 Temperature_Celsius: Thermal health changed from 110% (40°C) to 112% (38°C)

Given that normalization is specified by vendors, smartmontools could also take into account that e.g. health below 90% is critical (for WD drives that would be 60°C) and also should reported as critical (WARNING, etc.).