After yum transaction (install/upgrade/remove),
yum-plugin-post-transaction-actions will execute script which trigger
qvm-sync-appmenus in dom0 (through qrexec).
THIS INTRODUCE NEW PREDEFINED COMMAND IN QREXEC
Processes in AppVM can ask qrexec-agent to send a
MSG_AGENT_TO_SERVER_TRIGGER_EXEC message to qrexec-daemon.
The latter will execute predefined program. It is useful for
the purpose of file copy; the predefined program will create
a connected qfile-daemon<->qfile-agent pair.
