pkgupdate: do not create reboot notification for non-root system

This skips content of create-notification reboot_required hook in case
if path to system is not /. Only currently running system should raise
reboot_required request.
7 jobs for pkgupdate-hooks-fix in 5 minutes and 55 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #297360
cppcheck

00:00:30

passed #297361
luacheck

00:00:28

passed #297358
system-tests

00:01:56

passed #297359
system-valgrind-tests

00:03:21

passed #297356
unit-tests

00:01:09

passed #297362
unit-valgrind-tests

00:02:33

failed #297357
unit-valgrind-tests

00:01:24