Adjust ppc64le raptor machine buildbot locks

Covering two aspects:

• [1] locks were not honored due to bad naming
• [2] supporting 6 builds in parallel is too much for a 16 proc machine

9 builds were found in parallel, none of which in Acquiring locks status.

$ hostname && nproc && cat /proc/meminfo | grep MemTotal  && uptime

us-raptor-bbw1-p9

16

MemTotal:       66525184 kB

 06:53:48 up 13 days, 23:00,  1 user,  load average: 41.00, 49.87, 57.93

$ docker ps | wc -l

9

Adjusting locks to 3 is more realistic given that every builder requests 7 jobs. Accounting for the average where sometimes just 1 core is used during package build.