This seems to be inline with Busybox init, SysV init and, according
to the comments in code, the intended behaviour of Finit.
The effect is that `SIGPWR` will lead to Finit issuing the syscall `reboot`
with `cmd` parameter set to `RB_POWER_OFF` (rather than `RB_AUTOBOOT`), which
in turn will lead to a halt rather than a reboot.
The effect of the above inside a PID namespace other than the initial PID
namespace is that `wait` inside the parent of Finit will report that Finit was
killed with a `SIGINT` signal rather than `SIGHUP`.
The remaining sleep time returned by sleep is not accurate enough to be
used as a means to achieve "signal safe"-sleep. nanosleep can be used
in similar fashion instead and is granular enough for our purposes.
This issue was identified during reboot, when Finit is bombarded with
SIGCHLD, aborting the sleep that we do to give daemons a chance to shut
down gracefully. The total delay ended up being less than a second when
in fact two seconds were the intended delay.
Jacques de Laval