Fix random failure on getusage-missing environments
Fix random failure on getusage-missing environments

`* 1e6` makes a spurious result about floating point number's precision.

```
irb(main)[01:0]> 16.028
=> 16.028
irb(main)[02:0]> (16.028 * 1e6)
=> 16027999.999999998
```

ruby/spec,nobu/rubyspec,ruby/spec,eregon/rubyspec,eregon/rubyspec,ruby/spec,nobu/rubyspec,nobu/rubyspec,eregon/rubyspec