Improve description for cpu-rt-period,runtime daemon flags

These options configure the parent cgroup, not the default for containers,
nor the daemon itself, so adding that information to the flag description
to make this slightly more clear.

relates to 56f77d5ade945b3b8816a6c8acb328b7c6dce9a7 (#23430) which implemented
these flags.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cmd/dockerd/config_unix.go

@@ -54,8 +54,8 @@ func installConfigFlags(conf *config.Config, flags *pflag.FlagSet) error {
 	flags.IntVar(&conf.OOMScoreAdjust, "oom-score-adjust", -500, "Set the oom_score_adj for the daemon")
 	flags.BoolVar(&conf.Init, "init", false, "Run an init in the container to forward signals and reap processes")
 	flags.StringVar(&conf.InitPath, "init-path", "", "Path to the docker-init binary")
-	flags.Int64Var(&conf.CPURealtimePeriod, "cpu-rt-period", 0, "Limit the CPU real-time period in microseconds")
-	flags.Int64Var(&conf.CPURealtimeRuntime, "cpu-rt-runtime", 0, "Limit the CPU real-time runtime in microseconds")
+	flags.Int64Var(&conf.CPURealtimePeriod, "cpu-rt-period", 0, "Limit the CPU real-time period in microseconds for the parent cgroup for all containers")
+	flags.Int64Var(&conf.CPURealtimeRuntime, "cpu-rt-runtime", 0, "Limit the CPU real-time runtime in microseconds for the parent cgroup for all containers")
 	flags.StringVar(&conf.SeccompProfile, "seccomp-profile", "", "Path to seccomp profile")
 	flags.Var(&conf.ShmSize, "default-shm-size", "Default shm size for containers")
 	flags.BoolVar(&conf.NoNewPrivileges, "no-new-privileges", false, "Set no-new-privileges by default for new containers")