Jenkins.getComputers may be called frequently; do not perform an expensive locale-sensitive sort each time.

(Also relevant to JENKINS-22395 diagnostics.)

[FIXED JENKINS-22672] Make /threadDump easier to use.

[FIXED JENKINS-22688] Made graph font explicit and configurable

[FIXED JENKINS-22689] Show load statistics for master node

Instead, use a distance of 0.5x the width/height of the label.

This improves appearance in combination with JENKINS-22688 for
different font sizes.

Debian postinst: check for present user/group before adding them

pending was null as soon as task started running, so it was possible that another thread submits the task and have that executed while the first one was still running