Default WORKER_COUNT to 1 when cpu count is 1

[inket]

> let os = require('os')
undefined
> os.cpus()
[ { model: 'Intel(R) Xeon(R) CPU E5-2670 v2 @ 2.50GHz',
    speed: 2494,
    times: 
     { user: 379945100,
       nice: 8095800,
       sys: 53693800,
       idle: 67719016300,
       irq: 9700 } } ]
> 
> os.cpus().length -1 
0

😅

We shouldn't assume all CPUs are declared as multicore especially when running on virtual server environments.

[ljharb]

@goatslacker we should add a test for this.

[goatslacker]

Sure, we'd have to mock the os module. I felt like the cost of writing the test outweighed its benefits. I'm open to PRs though :)

[ljharb]

Fair point :-)