bug#38884: guix system roll-back doesn't roll setuid-programs back

[Brice Waegeneire via web]

Hello Guix,

"setuid-programs-service" extend the activation script which isn't loaded when 
rolling-back.

A difference between "reconfigure" and "switch-generation" (of which 
"roll-back" is just an useful alias) is that the former load the activation 
script (guix scripts system reconfigure switch-system-program) after switching 
the profile's symlinks and before installing the bootloader while the latter 
install the bootloader (guix scripts system switch-to-system-generation) then 
switch the symlinks (guix profiles switch-to-generation).  Fixing that could be 
done by loading the activation script after switching profiles, as 
"reconfigure" does.
I guess that loading the activation script again, on a already running running 
system, can have side effect but it shouldn't be an issue as it's already done 
by "reconfigure".

Cheers,
- Brice