- dynamically construct reference image on the target machine in a %post

- dynamically construct reference image on the target machine in a %post
  scriplet, instead of building it on the build machine. This solves a
  couple of problems:

  1. RPM databases constructed on a RH9 machine could be corrupt on a
     FC2 machine because of the LD_ASSUME_KERNEL rpm/glibc NPTL bug.
  2. vserver-reference is no longer a 50 MB download. The reference
     image can be installed from the localhost yum cache most of the
     time.

  But introduces a couple of problems:

  1. If the %post scriplet fails, the whole installation fails
     with a warning, but without an error. Not having a complete
     vserver-reference build is a bad thing.
  2. Must zap RPM and YUM locks while installing.