acquireSemaphore permit seems to be limited

Hi,
I am using the plugin in the following way
```groovy
def semaphore = createSemaphore permit:7

def s = [:]

for(int i = 0; i < 100; i ++)
{
def id="${i}"
s.put("semaphore" + id, { -> acquireSemaphore (semaphore){
sleep time:100,unit:"MILLISECONDS"
echo "semaphore" + id + " body"
}
})
}

parallel s
```

this seems to run only 3 processes concurrently not matter what the value of `permit` is. Is the number of concurrent steps limited by the cpu count or something else irrespective of the `permit` parameter ?

Thanks.