Run invirt-reload directly in the postinst of the fooconfig packages.

This replaces the old mechanism of using triggers. Activating triggers
via a package.triggers file doesn't seem to have taken off in the
Debian/Ubuntu communities.

Instead, the standard approach seems to be to run the triggered
command as usual, and add logic to the triggered command to postpone
actually running itself until later.

svn path=/trunk/packages/xvm-prodconfig/; revision=2940