allow re-exec'ing of msva, to facilitate upgrades
Currently, there is no mechanism to upgrade an existing msva instance in-place. Users need to log out and log back in to get it to upgrade.
Better would be to handle some user-supplied message (SIGHUP?) by re-execing the agent, but without re-spawning a new master subprocess.
(from redmine: created on 2010-10-10, closed on 2010-10-12)