Disable RT throttling

[shuhaowu]

See https://wiki.linuxfoundation.org/realtime/documentation/technical_basics/sched_rt_throttling.

Basically, the default /proc/sys/kernel/sched_rt_runtime_us means that there's a chance that the kernel would throttle/sleep a RT process once it uses up 950ms out of 1s of CPU time. This could result in deadline misses. The feature was implemented before the widespread availability of SMP and thus needed to avoid complete system lockup/denial-of-service. With multicore systems (especially with isolcpu), this shouldn't be needed.

Basically, we need a startup service that writes -1 to /proc/sys/kernel/sched_rt_runtime_us.

FYI: @carlossvg @LanderU

[carlossvg]

@shuhaowu I agree to disable it by default and add it to the configuration list in the documentation. I would put the script in the rt-configuration-scripts directory described in #26