Add synchronization between jobs and server closing

Fixes #5154
Daemon waiting 15 seconds for finishing server jobs before shutdown. In
this time it doesn't accept new jobs. After this time, it shutdown
despite running jobs.
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Add more required cgroup subsystems to check-config.sh (specifically, SCHED for cpu and CPUACCT for cpuacct)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Fix a few issues.

-single-dash => --double-dash for a few flags, and also there was a missing "B", as in "Container B".

Docker-DCO-1.1-Signed-off-by: Nathan LeClaire <nathan.leclaire@gmail.com> (github: nathanleclaire)
Merge pull request #6012 from tianon/check-config-cgroup-subsystems

Add more required cgroup subsystems to check-config.sh
Merge pull request #5952 from nathanleclaire/patch-2

Fix a few issues.
Merge pull request #5993 from LK4D4/fix_race_on_stop_#5154

Add synchronization between jobs and server closing