bug#50193: guix: shepherd pid 1 holds /dev/console

[muradm]

On IRC chat we identified an issue related to linux SAK, which
is explained here 
https://www.kernel.org/doc/html/latest/security/sak.html

Following the check what processes will be SAK'ed:

~# ls -l /proc/[0-9]*/fd/* | grep console
lrwx------ 1 root   root   64 Aug 24 21:22 /proc/1/fd/1 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 21:22 /proc/1/fd/2 -> 
/dev/console
l-wx------ 1 root   root   64 Aug 24 21:22 /proc/578/fd/4 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 21:22 /proc/593/fd/1 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 21:22 /proc/593/fd/2 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 20:03 /proc/705/fd/1 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 20:03 /proc/705/fd/2 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 21:22 /proc/909/fd/1 -> 
/dev/console
lrwx------ 1 root   root   64 Aug 24 21:22 /proc/909/fd/2 -> 
/dev/console

As it is seen from above output, pid 1 which is shepherd holds 
/dev/console
making linux SAK feature useless. When SAK command issued by 
shortcut keys,
all above proceses gets killed including pid 1 which is shepherd, 
causing
system to stall.