Fix autoinstall logic when configured memory is lower than needed

Fix autoinstall logic when configured memory is lower than needed

invirt-database: Fix the autoinstall logic so that if we've
increased the memory temporarily for the autoinstall above
the machine's database setting, we also bring maxmem up to
the same level.  Otherwise the machine doesn't turn on
because it's requesting to start with more memory than maxmem,
and this failure mode is silent to the user.