Reduce non-video job queue size from 320 to 144

Shortly the number of processes per server was increased from 5 to 12
(Ifc00708b8d), Asher, unaware of the reasons for a sudden increase in DB
problems caused by the job queue, introduced a limit in MySQL wikiadmin
connections of 80, to cause the job runners to fail if work is
concentrated on a single master. The current jobs-loop.sh goes into a
tight loop when faced with this failure scenario, and there have been
periods when 35 connection errors per second were logged.

Reduce the limit from 12 to 7 processes per server, and from 8 to 2
"immediate priority" processes, so that the total number of processes
(144) will now fall under the newly-raised wikiadmin process limit of
200.

Change-Id: Ie5bb11b0ee41b31b0509cfead13edace83c088f4