rpm: skip systemctl daemon-reload if systemd is not running

Skip it in chroot or a container to not fail the RPM transaction. While
RPM says it's "non-crtitical error in the %post scriptlet", it does
consider RPM transaction as failed in the end.
Interestingly, that happens only on Fedora 43, earlier versions actually
do treat it as non-critical and consider RPM transaction successful.

Anyway, adjust to not fail the scriptlet and don't worry if the error
should be considered fatal or not.

QubesOS/qubes-issues#10102

Author: marmarek

rpm_spec/core-agent.spec.in

@@ -1304,7 +1304,7 @@ then
     changed=true
 fi
 
-if [ "x$changed" != "x" ]
+if [ "x$changed" != "x" ] && [ -e /run/systemd/system ]
 then
     systemctl daemon-reload
 fi
@@ -1334,7 +1334,7 @@ then
     changed=true
 fi
 
-if [ "x$changed" != "x" ]
+if [ "x$changed" != "x" ] && [ -e /run/systemd/system ]
 then
     systemctl daemon-reload
 fi