During the docker image download phase, 20 threads are
attempting to download the docker images. This activity
includes calls to docker-untar which has high cpu utilization.
Dropping this from 20 to 5.
Change-Id: I7d58fad81b7cc201ee95af6b1327f1dd1f5a5d69
Fixes-Bug: 1822697
Signed-off-by: Al Bailey <Al.Bailey@windriver.com>