procfs: don't count guest and guest_nice times twice

See the following kernel code snippet from
kernel/sched/cputime.c's account_guest_time():

    /* Add guest time to cpustat. */
    if (task_nice(p) > 0) {
        cpustat[CPUTIME_NICE] += cputime;
        cpustat[CPUTIME_GUEST_NICE] += cputime;
    } else {
        cpustat[CPUTIME_USER] += cputime;
        cpustat[CPUTIME_GUEST] += cputime;
    }

So the old sum was wrong as some time frames were counted
double in the `total` value.

The data will likely still deviate from PVE, but we should
check by how much, as this version does seem more accurate.
We can still fix it to just use the same math as pve if it
seems off.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

proxmox/src/sys/linux/procfs.rs

@@ -308,8 +308,6 @@ fn parse_proc_stat(statstr: &str) -> Result<ProcFsStat, Error> {
         + stat.irq
         + stat.softirq
         + stat.steal
-        + stat.guest
-        + stat.guest_nice
         + stat.idle;
 
     // returns avg. heuristic for the first request