Fix appliance build dependency problem

Fix appliance build dependency problem

The appliance was being completely rebuilt every time guestfsd was updated. This
was because make.sh depended on guestfsd, which it had to do because it
called update.sh to install guestfsd.

This fix removes the call to update.sh in make.sh, and therefore the dependency
on guestfsd. The Makefile already includes a rule to run update.sh when guestfsd
is updated, so this was unnecessary.