rpm: explicitly enable & start virtlogd on install

rpm: explicitly enable & start virtlogd on install

When installing the libvirt-daemon RPM, we have a %post rule to
enable the libvirtd.service, virtlockd.socket and virtlogd.socket
files. This is only done, however, when the RPM is first installed,
not when upgrading RPMs. So virtlogd will not get activated on
upgrading, which is a problem as libvirt qemu driver will expect
it to be available by default.

This adds a trigger that is run when uninstalling libvirt-daemon
older than 1.3.0 that will enable & start virtlogd.socket if
libvirtd is enabled and/or started. Using the trigger rather
than %post ensures that it only runs once, allowing admins to
disable it explicitly thereafter without future upgrades
re-enabling it.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>