fedora: workaround slow system shutdown (#852)

It looks to be related to this report:
https://bugzilla.redhat.com/show_bug.cgi?id=1088619
Workaround idea was from comment 37.

The hanging process in Qubes VM is most likely dconf-service, but there
is a lot of possible causes. To start with a non-standard method of
accessing the X session (no real login manager, processes started by
qrexec-agent). So instead of wasting a lot of time on digging through
gnome services, simply shorten the stop timeout - the processes would be
killed anyway.

Makefile

@@ -68,6 +68,7 @@ install-rh:
 	install -D -m 0644 misc/yum-qubes-hooks.conf $(DESTDIR)/etc/yum/pluginconf.d/yum-qubes-hooks.conf
 	install -d -m 755 $(DESTDIR)/etc/pki/rpm-gpg
 	install -m 644 misc/RPM-GPG-KEY-qubes* $(DESTDIR)/etc/pki/rpm-gpg/
+	install -D -m 644 misc/session-stop-timeout.conf $(DESTDIR)/usr/lib/systemd/system/user@.service.d/90-session-stop-timeout.conf
 
 	install -D misc/qubes-core.modules $(DESTDIR)/etc/sysconfig/modules/qubes-core.modules
 	install -D misc/qubes-misc.modules $(DESTDIR)/etc/sysconfig/modules/qubes-misc.modules

misc/session-stop-timeout.conf

@@ -0,0 +1,2 @@
+[Service]
+TimeoutStopSec=500000us

rpm_spec/core-vm.spec

@@ -336,6 +336,7 @@ rm -f %{name}-%{version}
 %config(noreplace) /etc/yum.repos.d/qubes-r2.repo
 /etc/yum/pluginconf.d/yum-qubes-hooks.conf
 /etc/yum/post-actions/qubes-trigger-sync-appmenus.action
+/usr/lib/systemd/system/user@.service.d/90-session-stop-timeout.conf
 /usr/sbin/qubes-serial-login
 /usr/bin/qvm-copy-to-vm
 /usr/bin/qvm-move-to-vm