The local node name is heavily used in tracing, create a new global
variable to store it. Multiple goroutines can access it since it won't be
changed later.
The function used for getting host information
(host.SensorsTemperaturesWithContext) returns warnings in some cases.
Returning with error in such cases means we miss out on the other useful
information already fetched (os info).
If the OS info has been succesfully fetched, it should always be
included in the output irrespective of whether the other data (CPU
sensors, users) could be fetched or not.
Collection of SMART information doesn't work in certain scenarios e.g.
in a container based setup. In such cases, instead of returning an error
(without any data), we should only set the error on the smartinfo
struct, so that other important drive hw info like device, mountpoint,
etc is retained in the output.
We use multiple libraries in health info, but the returned error does
not indicate exactly what library call is failing, hence adding named
tags to returned errors whenever applicable.
