Previously, if `cpu.max` file has only `max` resource defined without
`period`, it was parsed incorrectly and silently drop error. While this
syntax is valid and actually used by some container runtimes. If period
is not defined, default value for it 100_000 must be used.
This commit fixes parsing function by using default value for period.
In addition, it adds zero value check, which fixes possible panic if
period has 0 value.
Related issue:
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/8808