Use a lower number of workers rather than the default value, which is
equal to the number of the cpu. Otherwise, in a multi cpu environment,
the number of the processes will very high.
In this PS, we use min(5, << number of cpu >>) as the default worker
count.
Closes-Bug: #1582254
Change-Id: I1c32cf0db794b43b8fb8be18f39190422ca5846f